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Documents: YM2413 Application Manual

YM2413 FM Operator Type-LL (OPLL) Application Manual

This document is an HTML conversion of these scans of an original document by Ricardo Bittencourt. This document typed by Maxim in 2003. Shading indicates additions/corrections/comments.

Table of Contents

  1. What is OPLL?
    1. Outline
    2. Features
    3. Sound Synthesis by FM
  2. Functions
    1. Primary Functions
    2. Pin Assignments
    3. Pin Functions
    4. Bus Control
    5. Channels and Slots
    6. Block Diagram
    7. Register Map
  3. Description of Operation
    1. Registers
      1. TEST: Address [$0F]
      2. AM/VIB/EG-TYP/KSR/MUL: Address [$00~$01]
      3. KSL/TL/DC/DM/FB: Address [$02~$03]
      4. AR/DR: Address [$04~$05]
      5. SL/RR: Address [$06~$07]
      6. BLOCK/F-Number/SUS/KEY: Address [$A0~$B8]
      7. RHYTHM: Address [$0E]
      8. INST/VOL: Address [$30~$38]
    2. Phase Generator (PG)
    3. Envelope Generator (EG)
    4. Operator (OP) and DAC
  4. Interfacing
    1. Clock Generation
    2. Audio Output Interface
    3. Interfacing Microprocessor/Microcomputer
  5. Synthesis of Music Sounds
    1. Procedure of Synthesizing Sounds
    2. Fundamentals of Sound Synthesis
    3. Examples of Sound Synthesis
    4. Procedure of Percussion Sound Synthesis
  6. Electrical Characteristics
  7. Timing Diagrams
  8. Outline Dimensions

Original page numbers

1 - 2 - 3 - 4 - 5 - 6 - 7 - 8 - 9 - 10 - 11 - 12 - 13 - 14 - 15 - 16 - 17 - 18 - 19 - 20 - 21 - 22 - 23 - 24 - 25 - 26 - 27

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I. What is OPLL?

(I-1) Outline

This LL-Type FM Operator incorporates a DA Converter and a Quartz Oscillator in addition to a YAMAHA original FM Sound Generator, allowing for a much easier and more economical sound generating system assembly than conventional LSIs. Tone data are stored in ROM for software simplicity, making it possible to execute data alterations involved in tone changes with just one Instruments selection operation. Furthermore, a built-in Tone Data Register with capacity to store one tone allows for the generation of sound effects and original tones. Tones applicable to the “CAPTAIN” and TELETEXT are included among built-in tone data.

(I-2) Features

(I-3) Sound Synthesis by FM

This is a method that makes use of harmonics generated by modulation to synthesize musical sounds. Circuitry to realize this method is relatively simple and is capable of generating waveforms including high order harmonics and un-harmonious sounds. It is known that relationships between the modulation index and the spectrum of harmonics are so natural that it is possible to synthesize a wide variety of sounds from natural musical instruments to artificial sounds.

This method is expressed with four parameters as follows.

(1) F = A sin (ωct + I sin (ωmt))

Where A is the amplitude of output, I modulation index, ωc and ωm angular frequencies of carrier and modulator respectively. The equation (1) can be expressed alternately as follows.

(2) F = A (J0(I) sin (ωct) + J1(I) (sin ((ωc + ωm) t) - sin ((ωc - ωm) t) + J2(I) (sin ((ωc + 2ωm) t) - sin ((ωc - 2ωm) t) + ...

Where Jn(I) is the nth-order Bessel function of the first kind. The amplitude of each harmonic component is expressed as a Bessel function of the modulation index. Sound synthesis by FM is found to be useful to obtain specific musical sounds or sound effects. String sounds, however, cannot be obtained as the distribution of harmonics is not uniform. A method called

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“Feedback FM” has been incorporated to solve the problem. This method is characterized by the following equation:

(3) F = A sin (ωct + βF)

Where β is the rate of feedback. The spectrum of harmonics produced by “feedback FM” has a saw-tooth waveform and therefore it can be used to synthesize string sounds.

Three function blocks, as follows, are needed to realize the above method of sound synthesis by FM.

  1. Phase generator (PG) generating ωc
  2. Envelope generator (EG) generating amplitude A and modulation index (I) which vary with time
  3. Sin table (SIN)

The method of sound synthesis by FM can be realized by Figure I-1 with units (operator cells) which combine the three function blocks. By this method, all we have to do is to define a frequency parameter and EG parameters.

Figure I-1 Sound synthesis by FM with units

II. Functions

(II-1) Primary Functions

This OPLL is an FM Sound Generator LSI with a built-in 9-Bit DA Converter. It has two sound generation modes: 9 melody sounds or 6 melody sounds plus 5 rhythm sounds, both allowing for simultaneous generation of different tones, Selection between these two modes can be performed from the software. One of the special features of the LSI is its built-in Instruments ROM. As shown in the table hereunder, this ROM incorporates 15 melody tones and 5 rhythm tones, as well as all tones used for “CAPTAIN” and TELETEXT. Furthermore, a built-in Tone Register with capacity to store one tone allows for the creation of sound effects and original sounds. By controlling the parameters of this register (E, ω1, I and ω2 in the equation below), all kinds of harmonics can be created on the basis of the sample wave ω1.

FM = E sin (ω1t + I sin (ω2t))

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Unlike conventional FM sound generators, this OPLL has a built-in Instruments ROM, permitting a substantial simplification of sound generation commands from the processor. First, the desired Instruments code is stored in the Instruments Selection Register. Then, after data has been input at the fixed intervals and timing, the unit starts generating sound. Automatic Processor play can be easily performed by writing data appropriate to the desired music into the Sustain and Volume registers. For using an original tone, the Instruments Selection Register must be cleared after writing data into the Tone Register as explained above. Rhythm sounds are generated by turning ON or OFF the corresponding bits in the Rhythm Control Register. In this case, the specified data must be input into the Key ON/OFF and F-Number Registers 8CH and 9CH.

(II-2) Pin Assignment

(II-3) Pin Functions

Symbol I/O Function
XIN I A quartz oscillator (3.579545 MHz) is connected between these two points.
XOUT O
D0~D7 I/O 8-Bit Data Bus for OPLL control.
A0 I For controlling the D0~D7 Data Bus.
CSWEA0
000Writes register address into OPLL.
001Writes register contents into OPLL.
010Outputs OPLL test data to D0, D1 pins. Normally not used.
011OPLL Data Bus high impedance
1**OPLL Data Bus high impedance
CS
WE
IC I Resets the system when the level is low, clearing OPLL Registers.
MO O Melody (MO) and Rhythm (RO) outputs. Both outputs are source followers. Integrated circuitry and an amplifier are necessary for subsequent processing.
RO
VCC I +5V Power Pin.
GND - Ground Pin.

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(II-4) Bus Control

The signals CS, WE and A0 provide control in the data bus for items such as addressing the register in OPLL and read/write of the data. Namely, they select one of the four operating modes as follows.

Table II-1 Mode selection

CS WE A0
1 1 * * Inactive mode
2 0 0 0 Address write mode
3 0 0 1 Data write mode
4 0 1 0 Bus inhibited
  1. Inactive mode
    The bus lines (D0~D7) are at high impedance while CS is ‘1′.
  2. Address Write mode
    When writing an address, set the control signals to the address write mode and place the address data on the data bus. The address of the specified internal register is now ready to receive data. After writing an address, be sure to wait 12 cycles of the master clock (øM) before writing in sound data.
  3. Data write mode
    When the control signals as (are) set for the data write mode, the data existing on the data bus enters the register of the given address. Wait for 84 cycles of the master clock (øM) before writing in further data or another address.
  4. Bus inhibited
    In this mode, the data of (on) the data bus is meaningless and uncontrollable.

Take note of the following regarding the address/data modes.

OPLL needs a certain length of wait time between successive writings of addresses or data into the registers. The wait time varies between address and data write modes. The processor waits for a time in Table II-2 before OPLL performs another function. If the wait time is not observed data will be uncertain.

Table II-2 Wait times

Mode Wait time
Address write 12 cycles
Data write 84 cycles

Note: the wait times are given in cycles of the master clock.

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(II-5) Channels and Slots

OPLL can produce nine channels of FM sounds as it has two operator cells per channel. However, the FM Generator system has only one operator cell, therefore, calculation for nine channels of FM sound is performed by passing through the operator cell 18 times. The order (slot number) of the pass through the operator cell corresponds to the register number. Control of the sound production is effected by controlling the register associated with the slot.

Channel data, like the F-number, controls two slots, No. 1 and 2.

In FM mode, the No. 1 slot handles the modulating waves and the No. 2 slot the carrier. The No. 1 slot can also be set for feedback FM mode. See (III-1-3) for setting this mode.

Table II-3 Channels and slots

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 Slot No.
1 2 3 1 2 3 4 5 6 4 5 6 7 8 9 7 8 9 Channel No.
1 2 1 2 1 2 Slot No. when a channel is seen
20 21 22 20 21 22 23 24 25 23 24 25 26 27 28 26 27 28 Relationship between the data of each channel and the register. (Example $20 to $28)

(II-6) Block Diagram

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(II-7) Register Map

Address D7 D6 D5 D4 D3 D2 D1 D0
00 AM VIB EG-TYP KSR MUL User Tone Register

(c):Carrier
(m): Modulator
01
02 KSL TL
03 DC DM FB
04 AR DR
05
06 SL RR
07
0E R BD SD TOM T-CY HH Rhythm Control
0F TEST OPLL Test Data (Normal ‘0′)
10~18 F-Num. 0~7 F-Number LSB 8 bits
20~28 SUS ON/OFF KEY ON/OFF BLOCK 0~2 F-Num. 8 F-Number MSB, octave set
Key ON/OFF register
Sustain ON/OFF register
30~38 INST VOL Instruments Selection and Volume Register

Register map for Rhythm mode (addr. $0E D5 = ‘H’)

Address D7 D6 D5 D4 D3 D2 D1 D0
36 BD-VOL Rhythm volume register
37 HH-VOL SD-VOL
38 TOM-VOL T-CY-VOL

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Register Contents

Address Bit
1 00 (m)
01 (c)
D7 Amplitude modulation ON/OFF switch
D6 Vibrato ON/OFF switch
D5 Sustained tone/decaying tone switch. 0: Percussive tone 1: sustained tone
D4 RATE key scale
D0~D3 Controls Multiple sample wave-harmonics relationship
2 02 (m)
03 (c)
D6 D7 LEVEL key scale
3 02 D0~D5 Modulator total level. Modulation index control
4 03 D4 (c)
D5 (m)
Carrier and modulated wave distortion waveform (flat wave rectification) ON/OFF switch
D0~D2 FM feedback constant (m)
5 rowspan=2:)04 (m)
05 (c)
D4~D7 Attack envelope change rate control
D0~D3 Decay envelope change rate control
6 06 (m)
07 (c)
D4~D7 Indication of decay-sustain level
D0~D3 Release envelope change rate control
7 0E D5 Rhythm sound mode selection. 1: Rhythm sound mode 0: Melody sound mode
D0~D4 Rhythm instruments ON/OFF switch
8 10~18 D0~D7 F-Number LSB 8 bits
9 20~28 D5 Sustain ON/OFF switch
D4 Key ON/OFF switch
D1~D3 Octave setting
D0 F-Number MSB
10 30~38 D4~D7 Instruments selection
D0~D3 Volume data

Tone Data

INST Instrument
0 Original
1 Violin
2 Guitar
3 Piano
4 Flute
5 Clarinet
6 Oboe
7 Trumpet
8 Organ
9 Horn
10 Synthesizer
11 Harpsichord
12 Vibraphone
13 Synthesizer Bass
14 Acoustic Bass
15 Electric Guitar
BD Bass Drum
SD Snare Drum
TOM Tom-tom
T-CY Top Cymbal
HH High Hat

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III. Description of Operation

All functions of the OPLL are controlled by data written in a register array by the processor. The data specifies the sound envelope shape, the degree of modulation, frequency, and output mode, etc. A complete set of data defines the sound as that of a piano or violin, etc. For the use of complex varieties of data sets se “Synthesis of music sounds”.

(III-1) Registers

A register comprises an area of 271 bits, as shown in the address map II-7. The address referred to here is the sub-address assigned to each operator of the OPLL. Musical sound data will be written into a register referred to by the sub-address. To store a data in the OPLL, we send a sub-address and then the sound data. If we access a location having the same sub-address many times, we only have to send the sub-address the first time. In subsequent accesses, we can send sound data alone to renew old data.

All registers are cleared to 0 by initialization (initial clear IC terminal = 0).

(III-1-1) TEST: Address [$0F]

This address is established to test the LSI.

Normally all addresses are 0.

(III-1-2) AM/VIB/EG-TYP/KSR/MUL: Address [$00~$01]

This register controls the multiplying factor that converts F-number into the carrier ($01) and modulator ($00) frequencies which matches the sound frequency components, and the envelope shape etc.

D7 D6 D5 D4 D3 D2 D1 D0
AM VIB EG-TYP KSR MUL
23 22 21 20

<Example>

F(t) = E sin (ωft + I sin (7 ωft))

  • Frequency according to F-number = ωft
  • Carrier MUL = 1
  • Modulator MUL = 7

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Table III-1 Multiplying factors

MUL Multiplying factor
0 ½
1 1
2 2
3 3
4 4
5 5
6 6
7 7
8 8
9 9
A 10
B 10
C 12
D 12
E 15
F 15

Since almost all musical steps become high for natural instruments, the sound can quickly change to high or low. This is accomplished by the key scale of RATE. Values in Table III-2 include the speed offset for the musical steps. Therefore, the actual RATE set for the ADSR will be these values which include the offset.

RATE = 4 × R + Rks

  • R is the set value for ADSR
  • Rks is the key scale offset value
  • Note that when R=0, RATE=0

Table III-2

0 1 2 3 4 5 6 7 Octave
0 1 2 3 4 5 6 7 BLOCK Data
0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 F-Num MSB
0 0 0 0 1 1 1 1 2 2 2 2 3 3 3 3 D4 = 0 key scale
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 D4 = 1 key scale

When D5 = ‘0′ it will be percussive tone. When D5 = ‘1′ it will be sustained tone. These sound modes are different in that the RELEASE RATE usage differs. The difference is shown in Figure III-1.

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Percussive tone (D5 = 0)

Sustained tone (D5 = 1)

Fig. III-1

(III-1-3) KSL/TL/DC/DM/FB: Address [$02~$03]

Total Level is used to control the modulation index (tone) by adding attenuation to the output of the envelope generator. Level key scale (KSL) ensures, like the key scale of RATE, that the output level of natural instruments falls as the pitch of sound rises.

D7 D6 D5 D4 D3 D2 D1 D0
$02 KSL TL
$03 DC DM FB

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Table III-3 Total level

D5 D4 D3 D2 D1 D0
Attenuation level 24 dB 12 dB 6 dB 3 dB 1.5 dB 0.75 dB

Table III-4

D7 D6 Attenuation rate
0 0 0 dB/oct
1 0 1.5 dB/oct
0 1 3 dB/oct
1 1 6 dB/oct

Table III-5 Attenuation at each F-Number at 3 dB/OCT

OCT F-Number
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15
0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
1 0 0 0 0 0 0 0 0 0 0.75 1.125 1.5 1.875 2.25 2.525 3
2 0 0 0 0 0 1.125 1.875 2.525 3 3.75 4.125 4.5 4.875 5.25 5.625 6
3 0 0 0 1.875 3 4.125 4.875 5.625 6 6.75 7.125 7.5 7.875 8.25 8.625 9
4 0 0 3 4.875 6 7.125 7.875 8.625 9 9.75 10.125 10.5 10.875 11.25 11.625 12
5 0 3 6 7.875 9 10.125 10.875 11.625 12 12.75 13.125 13.5 13.875 14.25 14.825 15
6 0 6 9 10.875 12 13.125 13.875 14.825 15 15.75 16.125 16.5 16.875 17.25 17.625 18
7 0 9 12 13.875 15 16.125 16.875 17.625 18 18.75 19.125 19.5 19.875 20.25 20.625 21

Unit: dB

Notes:

  • F-Number is the value of the four MSBs.
  • Half of the above data at 1.5 dB/oct
  • Double of the above at 6 dB/oct

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Table III-6 Modulation index

0 1 2 3 4 5 6 7
Modulation index 0 π/16 π/8 π/4 π/2 π

(III-1-4) AR/DR: Address [$04~$05]

Attack Rate defines the attack time of the sounds, and Decay Rate the decay time. The Rates are set as given in Table III-7.

D7 D6 D5 D4 D3 D2 D1 D0
AR DR
$04 23 22 21 20 23 22 21 20 Modulator
$05 23 22 21 20 23 22 21 20 Carrier

(III-1-5) SL/RR: Address [$06~$07]

Sustain Level is the critical point that, when sustaining sound has been attenuated to the prescribed level, the level is maintained thereafter. With percussive tone, it is the critical point of change from decay mode to release mode.

Release Rate is the disappearing rate of sustaining sounds after key OFF. For percussive tone, attenuation above the sustain level is expressed with decay rate and attenuation below the sustain level with release rate.

D7 D6 D5 D4 D3 D2 D1 D0
SL RR
$06 24 dB 12 dB 6 dB 3 dB 23 22 21 20 Modulator
$07 24 dB 12 dB 6 dB 3 dB 23 22 21 20 Carrier

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Table III-7 Attack and decay times in relation to RATE

RATE given below is that of the after key scale. RATE = RM × 4 + RL

RATE EG decay time EG attack time
RM RL 0 dB - 40 dB 10% - 90% 0 dB - 40 dB 10% - 90%
15 3 1.27 0.52 0.00 0.00
15 2 1.27 0.52 0.00 0.00
15 1 1.27 0.52 0.00 0.00
15 0 1.27 0.52 0.00 0.00
14 3 1.47 0.60 0.14 0.10
14 2 1.71 0.60 0.18 0.12
14 1 2.05 0.82 0.22 0.14
14 0 2.55 1.03 0.28 0.18
13 3 2.94 1.21 0.30 0.22
13 2 3.42 1.37 0.34 0.22
13 1 4.10 1.65 0.42 0.26
13 0 5.11 2.05 0.50 0.32
12 3 5.87 2.41 0.54 0.36
12 2 6.84 2.74 0.60 0.38
12 1 8.21 3.30 0.70 0.44
12 0 10.22 4.10 0.84 0.54
11 3 11.75 4.03 0.97 0.64
11 2 13.60 5.47 1.13 0.72
11 1 16.41 6.60 1.37 0.84
11 0 20.44 8.21 1.69 1.09
10 3 23.49 9.65 1.93 1.29
10 2 27.36 10.94 2.25 1.45
10 1 32.03 13.19 2.74 1.69
10 0 40.07 16.41 3.30 2.17
9 3 46.99 19.31 3.86 2.57
9 2 54.71 12.80 4.51 2.98
9 1 65.65 26.39 5.47 3.30
9 0 81.74 32.03 6.76 4.34
8 3 93.97 38.62 7.72 5.15
8 2 109.42 43.77 9.01 5.79
8 1 131.31 52.78 10.94 6.76
8 0 163.49 65.65 13.52 8.69
7 3 187.95 77.24 15.45 10.30
7 2 218.84 87.54 18.02 11.59
7 1 262.61 185.56 21.00 13.52
7 0 326.98 131.31 27.03 17.30
6 3 375.98 154.40 30.90 20.60
6 2 437.69 175.07 36.04 23.17
6 1 525.22 211.12 43.77 27.03
6 0 653.95 262.61 54.87 34.76
5 3 751.79 308.96 61.79 41.19
5 2 875.37 350.15 72.89 46.34
5 1 1050.45 422.24 87.54 54.07
5 0 1307.91 525.22 108.13 69.51
4 3 1503.58 617.91 123.50 82.39
4 2 1750.75 700.30 144.48 92.69
4 1 2180.89 844.40 175.07 108.13
4 0 2615.82 1050.45 216.27 139.63
3 3 3007.16 1235.82 247.16 164.70
3 2 3501.49 1400.60 280.36 185.37
3 1 4201.79 1680.95 358.15 216.27
3 0 5231.64 1280.89 432.54 278.06
2 3 6014.32 2471.64 494.33 329.55
2 2 7002.98 2801.19 576.72 370.75
2 1 8403.58 3377.91 780.30 432.54
2 0 10463.30 4201.79 865.88 556.12
1 3 12078.66 4943.20 988.66 659.11
1 2 14606.80 5602.39 1153.43 741.49
1 1 16807.20 6755.82 1400.60 865.80
1 0 20926.60 8403.58 1730.15 1112.24

Likely transcription errors here, especially lower in the table

Note: When RATE is ‘0′, the envelope will not change.

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(III-1-6) BLOCK/F-Number/SUS/KEY: Address [$A0~$B8]

Data defining a musical scale and interval. The F-Number is contained in the registers $1* and $2*.

D7 D6 D5 D4 D3 D2 D1 D0
$10~$18 F-Number
27 26 25 24 23 22 21 20
$20~$28 SUS KEY BLOCK F-Num
22 21 20 28

F-Number/Block

The OPLL generates the necessary frequency when an appropriate increment of phase is given. The increment is determined by the F-Number, Block, and Multiple information. The following formula gives the increment for a desired frequency.

(1) ΔP = fmus × 218 / fsam

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Because the increment value specification occupies many bits, we can give the increment within an octave and shift the value to double, 4 times, etc. for a specific octave. Then the instrument is expressed as follows.

(2) ΔP = 2B × F’ × MUL

From equation (1) and (2) the increment (F’) is expressed with 1 bit. F-Number and Block are expressed as follows.

F = (fmus × 218/fsam) / 2b-1 @ MUL = 1

Table III-8-1 F-Number (1)

Sound steps Frequency (4 oct) F-Number $2* $1*
D0 D7 D6 D5 D4 D3 D2 D1 D0
C# 277.2 181 0 1 0 1 1 0 1 0 1
D 293.7 192 0 1 1 0 0 0 0 0 0
D# 311.1 204 0 1 1 0 0 1 1 0 0
E 329.6 216 0 1 1 0 1 1 0 0 0
F 349.2 229 0 1 1 1 0 0 1 0 1
F# 370.0 242 0 1 1 1 1 0 0 1 0
G 392.0 257 1 0 0 0 0 0 0 0 1
G# 415.3 272 1 0 0 0 1 0 0 0 0
A 440.0 288 1 0 0 1 0 0 0 0 0
A# 466.2 305 1 0 0 1 1 0 0 0 1
B 193.9 323 1 0 1 0 0 0 0 0 1
C 523.3 343 1 0 1 0 1 0 1 1 1

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Table III-8-2 F-Number (2)

Sound steps Frequency (4 oct) F-Number $2* $1*
D0 D7 D6 D5 D4 D3 D2 D1 D0
G 392.2 257 1 0 0 0 0 0 0 0 1
G# 415.3 272 1 0 0 0 1 0 0 0 0
A 440.0 288 1 0 0 1 0 0 0 0 0
A# 466.2 305 1 0 0 1 1 0 0 0 1
B 493.9 323 1 0 1 0 0 0 0 1 1
C 523.3 343 1 0 1 0 1 0 1 1 1
C# 554.4 363 1 0 1 1 0 1 0 1 1
D 587.3 385 1 1 0 0 0 0 0 0 1
D# 622.2 408 1 1 0 0 1 1 0 0 0
E 659.3 432 1 1 0 1 1 0 0 0 0
F 698.5 458 1 1 1 0 0 1 0 1 0
F# 740.0 485 1 1 1 1 0 0 1 0 1

(III-1-7) RHYTHM: Address [$0E]

To control ON/OFF of the Rhythm mode selection and percussion instruments.

D5 D4 D3 D2 D1 D0
RHYTHM BD SD TOM TOP-CY HH

D0~D5 (RHYTHM): When D5 = 1, OPLL is in Rhythm mode with percussion sounds produced through channels 7~9 (see page 5). In this mode, the melody section is limited to six sounds. D0~D4 controls ON/OFF of percussion instruments. Therefore Key-ON bits $26, $27, $28 must always be cleared to 0. Slots 13~18 are related with percussion sounds as shown in Table III-9, and data of F-Num must input values that match percussion sounds.

Table III-9 Rhythm slots

Instrument Slot
BD 13, 16
SD 17
TOM 15
TOP-CYM 18
HH 14
Address Data
16 20
17 50
18 C0
26 05
27 05
28 01

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(III-1-8) INST/VOL: Address [$30~$38]

Determine the voice (15 voices preset in ROM and original voices) and the volume.

D7 D6 D5 D4 D3 D2 D1 D0
$30~$38 INST VOL

INST Instrument
0 Original
1 Violin
2 Guitar
3 Piano
4 Flute
5 Clarinet
6 Oboe
7 Trumpet
8 Organ
9 Horn
A Synthesizer
B Harpsichord
C Vibraphone
D Synthesizer Bass
E Acoustic Bass
F Electric Guitar

D3 D2 D1 D0
24 dB 12 dB 6 dB 3 dB

In the rhythm mode (addr = $0E, D5 = ‘H’), each rhythm volume for $36~$38 are set as follows:

Addr D7 D6 D5 D4 D3 D2 D1 D0
$36 BD
$37 HH SD
$38 TOM T-CYM

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(III-2) Phase Generator (PG)

The phase generator produces a phase value by accumulating increments that correspond to the frequency required at a given unit of time. The increment is generated from frequency data (F-Number, Block, and Multiple) sent from the registers. The frequency data is combined with the output of a built-in vibrato oscillator to produce a vibrato effect.

(III-3) Envelope Generator (EG)

The envelope generator (EG) varies tone and sound level with time under the control of Attack Rate, Decay Rate, Release Rate, Sustain Level and Total Level. Its dynamic range is 48 dB (resolution: 0.325 dB). EG uses a logarithmic scale and is represented with an attenuation level. The general waveform is shown in Figure III-2. Distinctively the waveform rises exponentially during attack time and varies linearly everywhere else. Attack stops and decay begins at 0 dB. Decay changes to sustain as soon as the sustain level is reached. Sustain will change to release when the key is released. The envelope waveform varies when parameters representing the effects of the total level, level key scale, and amplitude modulation, etc, are applied to EG.

Figure III-2 Envelope waveform

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(III-4) Operator (OP) and DAC

The operator performs FM calculations. Using the phase output from the phase generator, the operator calculates the value of SIN and multiplies it by the output of the envelope generator. Then if there are modulated waves, they are returned to the input of the operator and any sounds are sent to the DAC. This is controlled by the Feedback data.

The DAC performs DA conversion for all the sounds then outputs them as shown in Figure III-3 (a). To sum up the sounds, an integrated circuit is added to MO/RO. (Figure III-3 (b)) Since the level of percussive sounds seems lower, when compared to musical sounds, the same percussive sounds are output twice. (Figure III-3 (c))

Figure III-3

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IV. Interfacing

OPLL, controlled by a microprocessor or microcomputer, outputs an audio signal, being an analog signal converted with a D/A converter. To obtain sound from OPLL, it is necessary to interface it with other devices. This chapter describes interfacing.

Figure IV-1 System block diagram

(IV-1) Clock Generation

OPLL operates in the range of 2 to 4 MHz. Amplitude modulation, the frequency of the vibrato oscillator, and attack decay speeds are designed to take 3.6 MHz (3.579545 MHz) as the reference frequency. Therefore, when this LSI is used, it will be economical to connect the quartz crystal oscillator (for color burst signals) with Xin Xout.

(IV-2) Audio Output Interface

An external integrated circuit is needed for the OPLL’s music sound output, which is a pulse signal as described earlier. The output (and buffer) of this integrated circuit may be directly connected to an audio amplifier. For better sound quality, you can remove step noises by inserting a low-pass filter (cutoff frequency: 20kHz or so) between the integrated circuit and amplifier. Click noises accompanying power-ON/OFF will be necessary to protect the audion equipment (amplifier and speakers).

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Figure IV-2 Audio interface

(IV-3) Interfacing microprocessor/microcomputer

D0~D7 of OPLL are the bidirectional bus lines which connect to a processor. OPLL exchanges address and data with the processor. The bus control signals CS, WE and A0 control transfer of data. It is possible to build up an FM sound source system with the minimum configuration of OPLL, memory and processor.

Figure IV-3 Interfacing processor

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V. Synthesis of music sounds

This chapter describes what data to enter the OPLL registers in order to synthesize sound of the piano and brass.

(V-1) Procedure of Synthesizing Sounds

First, you have to analyze the sounds of the musical instrument which you want to synthesize by the FM method. For

example, the sound of a piano is characterized by a fast attack and, if the key is held down, a gradual delay. The will sound (sound will) include many overtones at the attack time however, as time elapses, overtones disappear, resulting in a different overtone composition. When you are aware (of) such characteristics, you are better able to synthesize the sounds by the FM method. The output amplitude can be determined from the characteristics of the envelope form and the modulation index from the overtone composition. Frequency ratio can also be determined roughly from the overtone composition because the frequency of the operator is related to it. In this way, you can determine the FM parameters roughly from characteristics of the sounds and, by listening to the synthesized sound, make minor corrections to obtain a more desirable result.

(V-2) Fundamentals of Sound Synthesis

The FM sound source makes use of carrier wave modulation by the modulator.

Since the FM’s basic parameter (carrier output level, modulator output level, modulator feedback level, carrier frequency, modulator frequency) is handled effectively, the pitch, tone and volume of sounds can all be decided. Table V-1 shows the relationship between FM parameters and OPLL parameters.

(V-3) Examples of Sound Synthesis

Table V-1 Fundamentals of sound synthesis

Item Related parameters MIN <- (Change of sounds) -> MAX
Output level of carrier TOTAL LEVEL (Data of A, D, S, R and key scale data) Low volume <-> High volume
Output level of modulator Dull sound <-> Bright sound
Feedback level of modulator FB Ordinary tone <-> Sharp tone (Noise)
Carrier frequency MULTI (BLOCK/F-Number) Low pitch <-> High pitch
Frequency of modulator Near overtone <-> Far overtone
  1. Electric piano
    • Determination of operator frequencies
      Set MUL to ‘1′, for both operators, to produce an overtone of higher frequency. (Increases are integer multiples)

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  • Output level of the operator
    Change the output of the modulator to adjust the tone. When determining the level of operator 1, adjust the sounds for rich overtones like those of the piano. Then make adjustment for sounds of higher frequencies by level scaling of operator 1. Level scaling is necessary so that the waveforms are nearly sine waves in high frequency ranges.
  • Setting EG
    Determine sound volume, tone, and envelope. Set operator 2 so that the sounds have a sharp attack and long sustain. (This can be set varying degrees.) Let operator 1, the modulator, produce many overtones at the attack time and later keep a certain composition of overtones unchanged. To adjust sound volume, apply key scaling to operator 2. Perform RATE scaling to make sounds of higher pitches sharp.
  • Readjustment of data
    Now sound synthesis is almost completed. Tones will vary somewhat depending on the setting of EG. Make a final adjustment with the output level and feedback level of the operators. If the sound is too metallic, for example, resuce the level of operator 1.
  • Adding effect
    Finally, add tremolo effect by LFO to simulate the sounds of the electric piano. This is possible by using the built-in amplitude modulation function or by refreshing the value of TOTAL LEVEL in intervals of 2~6Hz (possibly with triangular waves) by software.
  1. Trumpet
    • Output of operator
      Adjust the total level of operator 1, the modulator, at $10~$28 and the feedback level to the maximum of ‘7′ for bright tones.
    • Operator frequencies
      Set both operators at ‘1′.
    • EG
      Adjust two EGs for a slow attack. For brass sounds, ensure the modulator attack is slower than the carrier’s. This is necessary to express the characteristic attack of brass sounds.
    • Key scaling
      High-pitched sounds are not crisp because the envelope is set for a slow rise. Apply rate scaling for a more natural feeling of fast passages.

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  • LFO
    With a brass instrument, the pitch of long notes fluctuates a little even when a good player is playing. To express this, apply vibrato effect.

(V-4) Procedure of Percussion Sound Synthesis

Channels 7, 8 and 9 are used to synthesize percussion sounds. Five kinds of percussion sounds are generated by using these three channels and six slots. For the bass drum (BD), two slots are used to synthesize FM sounds. Therefore, bass drum sounds can be produced basically by the same procedure from (a) to (c). The other four kinds of percussion sounds (high hat, top cymbal, tom-tom, and snare drum) are described as follows.

OPLL includes a noise oscillator obtained by composing a white noise generator with several frequencies. This noise oscillator is specified by the frequency information (BLOCK, F-Number, Multiple) of the 8 and 9 channels. When composed with white noise, phase output suitable for percussion instruments is generated and given to the operator. Thus phases of four instruments are generated from two sets of frequency information. It is known empirically that the optimum ratio of two frequencies is 3:1 (f7CH = 3×f8CH). Now phase data of individual instruments are obtained. Next, we multiply this output with envelope information. Since the envelope is set as 1 slot -> 1 percussion instrument, values that reflect the characteristics of individual percussion instruments, as with melody instruments, are set in ROM. (Refer to III-1-7)

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VI. ELECTRICAL CHARACTERISTICS

1. Absolute Maximum Ratings

ITEM RATING UNIT
Pin voltage 0.3~7.0 V
Ambient operating temperature 0~70 °C
Storage temperature -50~125 °C

2. Recommended Operating Conditions

ITEM SYMBOL MIN. TYP. MAX. UNIT
Supply voltage VCC 4.75 5 5.25 V
GND 0 0 0 V

3. DC Characteristics

ITEM SYMBOL CONDITION MIN. TYP. MAX. UNIT
High level input voltage All input VIH 2.0 VCC V
Low level input voltage All input VIL -0.3 0.8 V
Leak input current A0, WE IL Vin = 0~5 V -10 10 µA
Three-state (off) input current D0~D7 ITSL Vin = 0~5 V -10 10 µA
Analog output voltage MO VMOA RLOAD = 2.2K 1.6 VPP
RO VROA RLOAD = 2.2K 1.6 VPP
Pullup resistance IC, CS RPU 100
Input capacity All input CI 10 pF
Output capacity All input CO 10 PF
Power current ICC 40 80 MA

4. AC Characteristics

ITEM SYMBOL CONDITION MIN. TYP. MAX. UNIT
Address setup time A0 TAS Fig. A-1 10 ns
Address hold time A0 TAH Fig. A-1 10 ns
Chip select write width CS TCSW Fig. A-1 80 ns
Write pulse write width WE TWW Fig. A-1 110 ns
Write pulse setup time WE TWS Fig. A-1 30 ns
Write data setup time D0~D7 TWDS Fig. A-1 10 ns
Write data hold time D0~D7 TWDH Fig. A-1 25 ns
Reset pulse width IC NICW Fig. A-2 80 Cycle

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5. DAC properties

ITEM SYMBOL CONDITION MIN. TYP. MAX. UNIT
Maximum output oscillation RO, MO Vout Fig. IV-2 2/5 VCC VPP
Resolution RO, MO Fig. IV-2 9 Bit
Noise RO, MO Fig. IV-2 -65 dB

Note: The noise level should be suitable for the volume level.

VII. Timing diagrams

Standard timing settings are VDL = 2.0V, VIL = 0.8V.

NOTE: TCSW, TWW and TWDH have been measured with either CS or WE high.

Fig. A-1 Write Timing

Fig. A-2 Reset Timing

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VII. OUTLINE DIMENSIONS

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