Texas Instruments MSP53C391 User manual

MSP53C391 and MSP53C392
Speech Synthesizers
User’s Guide
May 2000
SPSU016A
Printed on Recycled Paper

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Copyright 2000, Texas Instruments Incorporated

iii Read This First
Preface
Read This First
How to Use This Manual
This document contains the following chapters:
Chapter 1 –Introduction to the MSP53C391 and MSP53C392 Speech
Synthesizers
Chapter 2 –MSP53C391 Hardware Description
Chapter 3 –MSP53C392 Hardware Description
Chapter 4 –MSP53C391 and MSP53C392 Software Description
Appendix A –Editing Tools and Data Preparation
Appendix B –FM Synthesis
Appendix C –Listing of FMequM2.inc
Appendix D –MSP53C391/392 Timing Considerations
Appendix E –Listing of FM2INTR1.inc
Appendix F –MSP53C391 and MSP53C392 Data Sheet
Related Documentation From Texas Instruments
MSP50x3x Mixed-Signal Processor User’s Guide
(Literature Number SLOU006B)

iv

Contents
v
Contents
1 Introduction to the MSP53C391 and MSP53C392 Speech Synthesizers 1-1. . . . . . . . . . . . . .
1.1 Description 1-2. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1.2 Features 1-2. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1.3 MSP53C391 and MSP53C392 Comparison 1-3. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1.4 Pin Assignments and Description 1-4. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1.5 D/A Information 1-6. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1.6 Algorithms Supported 1-6. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2 MSP53C391 Hardware Description 2-1. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2.1 MSP53C391 Interface Overview 2-2. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2.2 Signal Description 2-3. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2.3 Master Microprocessor Interface Description 2-4. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2.3.1 Method 1: Polling 2-4. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2.3.2 Method 2: Interrupt 1 2-6. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2.3.3 Method 3: Interrupt 2 2-8. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2.4 Master Microprocessor Interface Timing 2-10. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2.4.1 Timing Method 1: Polling 2-10. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2.4.2 Timing Method 2: Interrupt 1 2-11. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2.4.3 Timing Method 3: Interrupt 2 2-12. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2.5 MSP53C391 Device Initialization 2-13. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
3 MSP53C392 Hardware Description 3-1. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
3.1 Interface Overview 3-2. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
3.2 Signal Description 3-3. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
3.3 Master Microprocessor Interface Description 3-4. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
3.3.1 Method 1: Polling 3-4. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
3.4 Master Microprocessor Interface Timing 3-7. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
3.4.1 Timing Method 1: Polling 3-7. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
3.5 MSP53C392 Device Initialization 3-8. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
4 MSP53C391 AND MSP53C392 Software Description 4-1. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
4.1 Software Overview 4-2. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
4.2 Command Sequence 4-2. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
4.3 Command Header 4-2. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
4.4 Data Streams 4-3. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
4.4.1 Synthesis Selection Codes 4-3. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Contents
vi
4.5 Command Sequences 4-4. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
4.5.1 Command Codes 4-5. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
4.5.2 Pin Expansion 4-5. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
4.5.3 Volume Control 4-6. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
4.5.4 Low-Power Sleep State 4-6. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
4.5.5 Request Software Version 4-6. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
4.5.6 Generate Test Signal 4-7. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
A Editing Tools and Data Preparation A-1. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
A.1 Editing Tools A-2. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
A.1.1 WINSDS A-2. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
A.1.2 SDS3000 A-2. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
A.2 Data Preparation A-3. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
A.2.1 LPC A-3. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
A.2.2 MELP and CELP A-3. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
A.2.3 PCM A-4. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
A.2.4 FM A-5. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
B FM Synthesis B-1. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
B.1 FM Synthesis Overview B-2. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
B.2 FM Synthesis Format and Commands B-2. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
B.2.1 Musical Notes B-3. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
B.2.2 Tempo Control B-3. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
B.2.3 Tempo Synchronization B-4. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
B.2.4 LOADTIMBRE Command B-4. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
B.2.5 Transposition B-5. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
B.2.6 DETUNE B-5. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
B.2.7 Adjust Output Volume B-5. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
B.2.8 Modulation Index Adjustment B-6. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
B.2.9 End of Song B-6. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
B.2.10 Command Summary B-7. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
B.3 FM Synthesis Data Structure B-9. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
B.4 Data Preparation of FM Synthesis B-12. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
B.4.1 MD2FM Software B-13. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
B.4.2 FM2MERGE Software B-14. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
B.4.3 Assembler B-15. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
C Listing of FMequM2.inc C-1. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
C.1 Listing of FMequM2.inc C-2. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
D MSP53C391/392 Timing Considerations D-1. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
D.1 General Constraints D-2. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
D.2 MSP53C391 Timing Waveforms D-3. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
D.3 MSP53C392 Timing Waveforms D-5. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Figures
vii Contents
E Listing of FMequM2.inc E-1. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
E.1 Listing of FM2INTR1.inc E-2. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
F MSP53C391 and MSP53C392 Data Sheet F-1. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
F.1 MSP53C31 and MSP53C32 Data Sheet F-2. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Figures
1–1 MSP53C391 Pin Assignments 1-4. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1–2 MSP53C392 Pin Assignments 1-5. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2–1 MSP53C391 Interfacing Diagram (Method 1: Polling) 2-4. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2–2 MSP53C391 Interfacing Diagram (Method 2: Interrupt 1) 2-6. . . . . . . . . . . . . . . . . . . . . . . . . . .
2–3 MSP53C391 Interfacing Diagram (Method 3: Interrupt 2) 2-8. . . . . . . . . . . . . . . . . . . . . . . . . . .
B–1 FM Conversion Process B-12. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Tables
1–1 MSP53C391 and MSP53C392 Comparison 1-3. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1–2 MSP53C391 Terminal Functions 1-4. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1–3 MSP53C392 Terminal Functions 1-5. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2–1 MSP53C391 Signal Description 2-3. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
3–1 MSP53C392 Signal Description 3-3. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
4–1 Speech Initiation Data 4-3. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
4–2 Synthesis Selection Codes 4-3. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
4–3 Command Sequence 4-4. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
4–4 Command Codes 4-5. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
4–5 Pin Expansion Command Codes 4-5. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
4–6 Volume Control Commands 4-6. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
4–7 Volume Control Code Ranges 4-6. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
B–1 Command Summary B-7. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

1-1
Introduction to the MSP53C391 and
MSP53C392 Speech Synthesizers
Topic Page
1.1 Description 1–2. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1.2 Features 1–2. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1.3 MSP53C391 and MSP53C392 Comparison 1–3. . . . . . . . . . . . . . . . . . . . . .
1.4 Pin Assignments and Description 1–4. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1.5 D/A Information 1–6. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1.5 Algorithms Supported 1–6. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Chapter 1

Description
1-2
1.1 Description
MSP53C391 and MSP53C392 are standard slave synthesizers from Texas
Instruments that accept compressed speech data from another microproces-
sor and produce speech with that data. This allows the MSP53C391 and
MSP53C392 to be used with a master microprocessor in the various speech
products including electronic learning aids, games, and toys.
The TI MSP53C391 and MSP53C392 support several different speech syn-
thesis algorithms to permit tradeoffs to meet the different price performance
requirements of different markets. They also incorporate a two-channel FM
synthesis routine for music generation.
Both the MSP53C391 and MSP53C392 are special programs that run on the
MSP50C3x device. For more information about the MSP50C3x, please refer
to the
MSP50x3x User’s Guide (literature number: SLOU006B)
1.2 Features
Wide ranges of algorithms are incorporated in one chip. This allows the
user to choose from a low bit rate to high-quality synthesizing routines for
their application. Algorithms included are:
LPC 5220, LPC D6
MELP v4.1
CELP v3.4, 4.2 kbps, 4.8 kbps, 6.2 kbps, 8.6 kbps, 10.7 kbps
8-bit PCM
FM II
Software selectable 8-kHz or 10-kHz speech sample rate
Three different interface options to support different pin count require-
ments
32-Ωspeaker direct drive capability
Internally generated clock requires no external components
Maximum 10-µA standby current in sleep mode
Digital volume control
Built-in, two general-purpose output pins for MSP53C391 pin expansion

MSP53C391 and MSP53C392 Comparison
1-3 Introduction to the MSP53C391 and MSP53C392 Speech Synthesizers
1.3 MSP53C391 and MSP53C392 Comparison
The MSP53C391 is optimized to support a 4-bit wide data transfer protocol.
The MSP53C392 is optimized to support an 8-bit wide data transfer protocol.
The use of the 4-bit wide protocol in the MSP53C391 frees up some I/O pins
thatcanbeusedforotherpurposes.Thesepins(EOSandBUSY)canbeused
to simplify the interface by minimizing the need to periodically poll the
MSP53C391 for its current status.
Theuseofthe8-bitwideprotocolintheMSP53C392providesamoreefficient
data transfer.
A detailed comparison of the two devices is listed in Table 1–1.
Table 1–1. MSP53C391 and MSP53C392 Comparison
MSP53C391 MSP53C392
Number of Data Lines 4 bit 8 bit
Number of Control Lines 2 (Strobe & R/W) 2 (Strobe & R/W)
Data Request Supported N/A
Separate EOS Line for Detecting
End-of-Speech Supported N/A
Pin Expansion Two expansion pins N/A

Pin Assignments and Description
1-4
1.4 Pin Assignments and Description
Figure 1–1 shows the pin assignments for the MSP53C391. Table 1–2 pro-
vides pin functional descriptions. Figure 1–2 shows the pin assignments for
the MSP53C392. Table 1–3 shows the pin functional descriptions.
Figure 1–1. MSP53C391 Pin Assignments
1
2
3
4
5
6
7
8
16
15
14
13
12
11
10
9
DATA2/EOS
DATA1
DATA0
OUT2
OUT1
EOS
R/W
OSC IN
DATA3/BUSY
STROB
IRQ
DAC+
DAC–
VDD
VSS
INIT
(TOP VIEW)
MSP53C391
N PACKAGE
Table 1–2. MSP53C391 Terminal Functions
PIN
I/O
DESCRIPTION
NAME NO.
I/O
DESCRIPTION
DAC+ 13 OD/A output. This output pulses high for positive output values. It remains low
when negative values are output.
DAC– 12 OD/A output. This output pulses high for negative output values. It remains
low when positive values are output.
DATA 0–3 3,2,1,16 I/O Data lines
EOS 6 O End of speech signal. Output high when end of speech is reached.
INIT 9 I Initializeinput.WhenINITgoeslow,theclockstops,theMSP53C391goesinto
low-power mode, the program counter is set to zero, and the contents of the
RAM are retained. An INIT pulse of 1 µs is sufficient to reset the processor.
IRQ 14 O Negative-edge trigger interrupt request line. Connect to the external inter-
rupt of the master MCU for interrupt mode operation.
OUT 1–2 5,4 O General-purpose output ports used for pin expansion
OSC IN 8 I This signal should be connected to VSS.
R/W 7 I Read/write select signal. Set high for read operations or cleared low for
write operations by the master processor.
STROB 15 IStrobe signal for read and write operations. Pulsed low for read or write
operations
VDD 11 –5-V nominal supply voltage
VSS 10 – Ground pin

Pin Assignments and Description
1-5 Introduction to the MSP53C391 and MSP53C392 Speech Synthesizers
Figure 1–2. MSP53C392 Pin Assignments
1
2
3
4
5
6
7
8
16
15
14
13
12
11
10
9
DATA6/EOS
DATA5
DATA4
DATA3
DATA2
DATA1
R/W
OSC IN
DATA7/BUSY
STROB
DATA0
DAC+
DAC–
VDD
VSS
INIT
(TOP VIEW)
MSP53C392
N PACKAGE
Table 1–3. MSP53C392 Terminal Functions
PIN
I/O
DESCRIPTION
NAME NO.
I/O
DESCRIPTION
DAC+ 13 OD/A output. This output pulses high for positive output values. It remains
low when negative values are output.
DAC– 12 OD/A output. This output pulses high for negative output values. It remains
low when positive values are output.
DATA 0–7 14,6,5,4,
3,2,1,16 I/O Data lines
INIT 9 I Initialize input. When INIT goes low, the clock stops, the MSP53C392 goes
into low-power mode, the program counter is set to zero, and the contents of
theRAMareretained.AnINITpulseof1µsissufficienttoresettheprocessor.
OSC IN 8 I This signal should be connected to Vss.
R/W 7 I Read/write signal
STROB 15 IStrobe signal for read/write
VDD 11 –5-V nominal supply voltage
VSS 10 – Ground pin

D/A Information
1-6
1.5 D/A Information
Two-PinPushPull(Option1)isselectedinMSP53C391andMSP53C392that
candirectly drive a32-Ωspeaker. Pleasereferto the MSP50x3xMixedSignal
Processor Users Guide (literature number: SPSU006B) for more information
on the D/A and amplifier circuit.
1.6 Algorithms Supported
LPC: D6 and 5220 format. Data rates 1.5 to 3 kbps at an 8-kHz sample
rate
MELP: Data rates range form 2kbps ~ 3.5 kbps at an 8-kHz sample rate
CELP: Data rates can be selected form 4.2 kbps ~ 10.7kbps at an 8-kHz
sample rate
PCM: 8 bit. Data rates is 64 kbps for 8 kHz sampling
FM: Frequency modulation for two-channel musical instrument
synthesis.

2-1
MSP53C391 Hardware Description
Topic Page
2.1 MSP53C391 Interface Overview 2-2. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2.2 Signal Description 2-3. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2.3 Master Microprocessor Interface Description 2-4. . . . . . . . . . . . . . . . . . . .
2.4 Master Microprocessor Interface Timing 2-10. . . . . . . . . . . . . . . . . . . . . . .
2.5 MSP53C391 Device Initialization 2-13. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Chapter 2

MSP53C391 Interface Overview
2-2
2.1 MSP53C391 Interface Overview
The MSP53C391 accepts data from the master microprocessor across four
data lines. The transfer of data is controlled by two control lines (R/W and
STROB). The data is loaded to an internal buffer and the synthesis process
reads the data from the internal buffer as needed. The MSP53C391 signals
that it is not ready to accept data when the buffer is full, or there is some other
condition that would prevent the MSP53C391 from accepting new data. This
signal is communicated to the master microprocessor using either the IRQ or
BUSY signals.
Depending on the number of available pins on the master microprocessor,
three different connection options are provided to connect the master micro-
processor to the MSP53C391. Whichever method is used, two operations
must be accomplished: 1) Determining if the MSP53C391 is ready to accept
new data, and if it is ready, 2) writing new data to the MSP53C391.
Twocontrollinesareprovidedtoenablethemastermicroprocessortoaccom-
plish these two tasks, STROB and R/W.
The R/W line determines whether a read or a write operation is done to the
MSP53C391 when the STROB is pulsed low. If the R/W is high, then a read
fromtheMSP53C391isdonewhentheSTROBispulsedlow.IftheR/Wislow,
then data is written to the MSP53C391 when the STROB is pulsed low.
TwosignalsareprovidedtodetermineiftheMSP53C391isreadyornotready
to accept new data. The BUSY signal shares the same pin as the DATA3 sig-
nal. During a read operation, this signal goes high to signal that the
MSP53C391 is ready for a write operation. If this signal is low during a read
operation, then the MSP53C391 is not ready for a write operation.
An alternative to polling the BUSY signal is provided by the IRQ signal. This
signal goes from high to low when the MSP53C391 is ready for a write opera-
tion.
TheEOSsignalindicateswhetherornottheend-of-speechhasbeenreached
bythesynthesisprocess.ItissethighbytheMSP53C391whenthestopcode
inthedatastreamisreached.Thissignalisprovidedontwopins.Itcanberead
directly on pin 6 (EOS), or during a read operation on pin 1 (DATA2/EOS).
Threemethods are providedfor interfacing theMSP53C391 to variousmicro-
processors. This allows the designer to make trade-offs between the number
of device pins being used and the algorithm complexity for the interface to the
master microprocessor.

Signal Description
2-3 MSP53C391 Hardware Description
2.2 Signal Description
Table 2–1. MSP53C391 Signal Description
Pin Description
Name No.
DAC+
DAC– 12 13 PDM-style DAC used for speech output.
DATA3/BUSY 16 BUSY signal can be obtained on DATA 3 during read operation. A high signal
indicates that the MSP53C391 is not busy and ready to accept data. A low signal
indicates that the MSP53C391 is busy and the master should not write any
command or data to MSP53C391.
DATA2/EOS 1The EOS signal can be obtained on the DATA2 pin during a read operation. This
signal is normally low, but goes high when the end-of-speech code is reached in
the data stream.
STROB 15 This is an active low strobe signal for the reading and writing operation from the
master microprocessor. The data to be read is available when the strobe is active
(low) for the read operation. The data on the data line is latched into the
MSP53C391 on the raising edge of the strobe signal for the write operation.
R/W 7Read/write signal from master microprocessor. A high signal for a read operation
and a low signal for a write operation.
IRQ 14 When the data latched into the MSP53C391 is read and the MSP53C391 device is
ready to accept more data, a negative edge interrupt signal is generated to
interrupt the master. For proper operation of the interrupt function, a negative edge
triggered external interrupt input pin is required on the master microprocessor.
EOS 6This is an active high output signal that is asserted when end-of-speech is
reached. It indicates that the speech synthesis process is finished. When a high is
detected on the EOS line by the master microprocessor, dummy bytes are written
to the MSP53C391 to reset the EOS. The next transfer can then be initiated after
the EOS was de-asserted. EOS also appears on the DATA2 pin during a read
operation for adopting different interfacing methods.
OUT1–2 5,4 General-purpose output port that can be controlled by the master microprocessor.
DATA 0–3 3,2,1,16 4-bit bidirectional data line
INIT 9Reset signal. A low pulse to reset the chip. It can also be used to stop the
MSP53C391 operation during speech synthesis. Following the rising edge of the
INIT pulse, a delay of up to 5 ms will be required to permit the MSP53C391 to com-
pletely initialize its internal condition.

Master Microprocessor Interface Description
2-4
2.3 Master Microprocessor Interface Description
2.3.1 Method 1: Polling
This method is used when it is important to minimize the total number of inter-
facepins between the mastermicroprocessor and the MSP53C391. A total of
threecontrollinesand4datalinesarerequiredforthismethod.Thetwostatus
bits can be read from the MSP53C391 by manipulating the R/W and STROB
lines and reading the data lines.
The interfacing diagram is shown in Figure 2–1:
Figure 2–1. MSP53C391 Interfacing Diagram (Method 1: Polling)
Output Port
Output Port
Output Port
I/O Port
I/O Port
I/O Port
I/O Port
STROB
R/W
INIT
DATA3/BUSY
DATA2/EOS
DATA1
DATA0
EOS
IRQ
15
7
9
16
1
2
3
DAC+
DAC– TO SPEAKER OR
AMPLIFIER/FILTER
MASTER
MICROPROCESSOR MSP53C391
13
12
6
14
NOTES: A. STROB: Active low strobe signal
R/W: Read/write signal
DATA 0–3: 4-bit data line
BUSY: Active lowbusy signalformMSP53C391.Ahighsignalindicatesthatthe MSP53C391is not busyand
is ready to accept data.
EOS: End-of-speech data. A high signal indicates end-of-speech. Two bytes of dummy data writen resets
the EOS to low.
INIT: Active low reset signal. The master microprocessor should issue a reset signal to MSP53C391 after
power up to properly initialize the MSP53C391 device.
B. When not being used, the EOS and IRQ pins should be left unconnected.

Master Microprocessor Interface Description
2-5 MSP53C391 Hardware Description
Read Operation
1) The master microprocessor sets R/W high to indicate a read operation.
2) The master microprocessor sets STROB to low and reads the state of
BUSY and EOS.
3) The master microprocessor sets STROB high.
If the BUSY signal was high in step 2, the MSP53C391 is not busy and is
ready to accept a write operation. If the BUSY signal was low in step 2, the
MSP53C391 is not ready to accept a write operation and the read operation
should be repeated until BUSY is asserted high.
If EOS was high in step 2, the synthesis process has reached the end of the
speech data stream. In this case, the master microprocessor should stop try-
ingtosenddataandresettheMSP53C391toallowittoacceptadditionalcom-
mands or synthesis data.
The frequency of the polling operation should be optimized to the data rate of
the algorithm being used to synthesize speech. If the polling operation is too
frequent, the MSP53C391 spends too much time servicing the polling opera-
tion and the quality of the synthetic speech may be affected. If the polling op-
erationistooinfrequent,theinternalbuffermayrunoutofdataandthesynthe-
sisprocesscanbecome corrupted.Normally,apollingfrequency of fourtimes
the bit rates of the speech data provides optimal transfer characteristics.
Example:
For 6.2 kbps CELP the frequency of polling would be
6.2
n4
n = the number of bits transfered at a time
Write Operation
1) The master processor should determine that the MSP53C391 is ready to
accept data by reading the BUSY signal as described previously.
2) The master microprocessor clears R/W low to indicate a write operation
3) The master microprocessor presents valid data to the four data pins
(DATA0 – DATA3).
4) The master microprocessor pulses the STROB signal low and then high
to latch the data to the MSP53C391 input data latch.
5) The master microprocessor should do a read operation to determine that
the MSP53C391 is ready to accept additional data before attempting to
write more data.

Master Microprocessor Interface Description
2-6
IftheEOSsignalisassertedhighduringthereadoperation,theend-of-speech
hasbeen reachedand a resetoperation shouldbe performedprior to sending
new commands or speech data. The reset can be done in one of two ways:
Pulsing the INIT pin low and then waiting for the MSP53C391 to re-initialize
itself or by writing two dummy bytes as described in the following.
RESET Operation
1) Perform a read operation to determine that both the EOS and BUSY sig-
nals are high.
2) If both the EOS and BUSY signals are high, write 2 bytes of dummy data
to the MSP53C391 by repeating the write operation four times as de-
scribed previously.
2.3.2 Method 2: Interrupt 1
In this method, the IRQ pin of the MSP53C391 is connected to an external in-
terrupt input pin of the master microprocessor. When the MSP53C391 is not
busyandisreadytoacceptdata,theIRQsignalgoeslowandprovidesanega-
tive edge to trigger an interrupt in the master processor. This minimizes the
need to constantly poll the MSP53C391 while waiting for it to become ready
to accept new data.
Figure 2–2. MSP53C391 Interfacing Diagram (Method 2: Interrupt 1)
Output Port
Output Port
Output Port
I/O Port
I/O Port
I/O Port
I/O Port
INT
STROB
R/W
INIT
DATA3
DATA2/EOS
DATA1
DATA0
IRQ
EOS
15
7
9
16
1
2
3
MASTER
MICROPROCESSOR MSP53C391
DAC+
DAC–
13
12
14
6
TO SPEAKER OR
AMPLIFIER/FILTER
NOTE A: IRQ: Negative edge interrupt to master microprocessor when MSP53C391 is not busy and ready to accept data.

Master Microprocessor Interface Description
2-7 MSP53C391 Hardware Description
Read Operation
1) The master microprocessor sets R/W high to indicate a read operation.
2) The master microprocessor sets STROB to low and reads the state of
BUSY and EOS.
3) The master microprocessor sets STROB high.
The EOS is used to signal that the end-of-speech has been reached. In this
case,themastermicroprocessorshould stop tryingtosenddataandact tore-
settheMSP53C391 so astoprepareittoacceptadditionalcommandsorsyn-
thesis data.
In this method, the BUSY signal is not normally used. Instead, the IRQ signal
is used to signal the need for new speech data. It pulses low then high to pro-
duce a negative edge signal to the master microprocessor when the
MSP53C391becomesreadytoacceptanewwriteoperation.Itwillremainlow
until a new nibble is written. The master microprocessor should immediately
initiateawrite operation whentheIRQsignalgoeslow.If themaster micropro-
cessordelays fortoolong atime beforewriting new data,it ispossible thatthe
buffer will empty and the synthesis process will be interrupted or the quality of
speech will be degraded.
Write Operation
1) Themastermicroprocessorshouldclearallpendinginterruptsandenable
the external interrupt.
2) The master microprocessor writes the first nibble of data by presenting
validdataonDATA0–DATA3,settingR/Wlowtoindicateawriteoperation
and pulsing STROB low and high to latch the data into the MSP53C391
input latch.
Subsequent data is written following the falling edge of the IRQ signal.
3) The master microprocessor waits for a falling edge on the IRQ signal.
4) Master microprocessor sets R/W high and pulses the STROB to read the
EOS signal.
5) The master microprocessor clears R/W low to indicate a write operation
6) The master microprocessor presents valid data (first nibble of the dummy
data if EOS is high or nibble of speech data if EOS is low) to the four data
pins (DATA0 – DATA3).