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People To People Technology
MSM9831
A Brief Application Note
Robert Brenner, DBG Marketing Communications
March 1998 October 1997
With the MSM9831 manufactured by Oki Electric Industry Co., Ltd., Japan, comes a low-cost speech synthesiser with integrated mask ROM designed for applications which demand high voice quality, but suffice with relatively short playback times. Integration of this small device into existing digital systems or new designs is a child's play.
Half the size of currently available LSIs of that kind, the Oki MSM9831 emits a wide variety of high quality natural sounds, and opens the door for LSIs to be included in a wide range of applications. The MSM9831 can be used in various applications including voice guidance systems, vehicle navigation systems, and mechanical sound effects for digital appliances to improve the functionality of many of the existing electronic equipment. As the world becomes increasingly digital, many of the sounds emitted by electronic appliances, sounds we have grown accustomed to, will begin to disappear. For example, think how strange it would be not to hear the steady clicking of your car's turn signal when it is activated. The MSM9831 has the ability to put sounds such as these back into electronic equipment, and allows manufacturers to make transition to digital technology as seamlessly as possible. the fixed 8-bit vertical resolution playback time and voice quality requirements can be selected to best suit a given application. For example at 8kHz sampling (64kbps bit-rate), the playback time is 6 seconds if the master clock is 4.096MHz. Table 1 has
Sampling Filter Cut-off Frequency Frequency
[kHz] [kHz] (-3dB)
input refers to the channel number to be played while 32 pulses reset the internal address counter. Playback then commences upon a rising edge of _ST. Playback is stopped by returning _ST to L without any pulse into _PI. _PDWN sets the device to standby mode. AOUT is an open drain N-MOS output which provides the filtered audio signal in the form of changing output currents. Signals cannot be picked before the filter. Cut-off frequency and output frequency characteristics vary proportionally with the sampling frequency applied (Figure 1). In
Playback Time
[sec]
4.0 5.3 6.4 8.0 10.6 12.8 16.0
1.2 1.6 2.0 2.5 3.2 4.0 5.0
11.8 8.9 7.4 5.9 4.4 3.7 2.9
FIGURE 1. Characteristic of the low-pass filter at 8KHz sampling
TABLE 1. Values specified are for 4.096MHz clock frequency and are based on 378kbit free ROM area. Playback times are obtained by: memory / (sampling rate * bit number).
Algorithm
Unlike other OKI speech products, the MSM9831 utilises 8bit Pulse Code Modulation (PCM) for the storage of speech data. Interestingly, the data is of nonlinear nature and provides a fidelity equivalent to 10-bit linear PCM for the mid range of waveforms. Consequently, the signal-to-noise ratio is significantly improved.
more details. In total, 31 playback channels can be addressed. Also incorporated on-chip are a 10-bit current-type DAC and a high quality low-pass filter. Providing a wide power supply range from +2.0 to +5.5V, the MSM9831 is suitable for both 3V and 5V platforms whilst drawing merely 2mA maximum at +5V or 1.0mA at +3V within an ambient temperature from -40 to +85 C.
Block Functions
Figure 2 shows the block schematic diagram unveiling the simple but effective design. A serial interface is provided to control all functions in conjunction with an MCU which needs to provide only three output ports. _PI is the address input pin through which the channel number to be replayed is defined by means of pulses while _ST is kept on L. The number of pulses
standby mode, AOUT assumes half level in that current continues flowing, but an internal canceller circuit prevents occurance of pop noise. The oscillator circuit (XT and _XT) can be used in two ways. A ceramic oscillator rating 3.5 to 4.5MHz (typically 4.096MHz) across XT and _XT provides the conventional means of operation. Additionally, an external clock can be input to XT while _XT is left open. The set of sampling frequencies will vary proportionally with the clock and therefore take influence on the playback time and quality.
Internal Mask ROM
The built-in 384KBit ROM reserves 2 Kbit area for a so-called Phrase Control Table, PCT, which allows the user to compile sentences consisting of preinstalled words with the same simple control as for individual word addressing. If sentences were stored as phrases they would occupy more memory since
Structure
With a set of selectable sampling frequencies ranging from 4 to 16kHz in 7 intervals and
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VDD ST PI PDWN Serial Control Interface 16-Bit Address Controller LPF GND AOUT
MCU
8 16
100nF VDD
8
P1.2 P1.1 P1.3
ST PI
VDD AOUT
PDWN
Timing Controller
10-Bit DAC
2Kbit Phrase Control Table 2Kbit Address ROM 2Kbit Test ROM 10
MSM 9831
GND
XT
XT
Oscillation Circuit
PCM Data Area 378KBit
8
PCM Synthesiser
PDWN
SOP8-P-250-1.27K (top view)
ST
XT
XT
FIGURE 2. Block diagram and pin assignment
ST PI GND AOUT
PDWN XT XT VDD
PI
AOUT
certain words have to be stored multiple times. Not only does the PCT reduce requirement for memory, but also it releaves the MCU considerably. Address The PCT is Words in ROM [Hex] addressable from 01 "it will be" 02 "sunny" 01h to 1Fh 03 "cloudy" corresponding to 04 "today" 05 "tomorrow" 31 channels. Up to 06 "partly" : eight word ROM
FIGURE 5. Principle playback and stop timing.
better memory economy and less MCU intervention compensate well.
Small Package
MSM9831 comes in a small SOP package measuring only 5 x 6.8mm by area with a maximum mounting profile of 2.05mm. The lead pitches are 1.27mm (50mils) and reflow soldering is applicable. This small package given and the few external components required make it easy and cost effective to realise speech add-ons to miniature digital electronic products.
Typical Application
The simple application of MSM9831 is illustrated by Figures 3 and 4 showing two means of oscillation and audio amplification. 1F 320ms silence In principle, playback is started Address ROM addresses assigned Sentence compiled [Hex] with the timing as 01 01 02 04 "it will be sunny today" displayed by Figure 02 01 03 05 "it will be cloudy tomorrow" 5. It is further 03 01 03 04 "it will be cloudy today" 04 01 02 1F 06 03 05 "it will be sunny, partly cloudy tomorrow" possible to re-input : an address whilst : playback is ongoing 1F TABLE 2. Example of ROM data and Phrase Control Table pattern. and of course to stop it when _ST is addresses can be assigned to any lowered for 0.35 to 2000s and of these addresses, including raised again. 350 s (@8kHz silence insertion from 32 to 996ms sampling frequency) after the in intervals of 32ms. Table 2 raising edge, playback will stop. shows a typical example. 100nF The small table contains word VDD phrases and their corresponding addresses as stored in the ROM. VDD P1.2 ST These addresses can be referred MCU P1.1 PI AOUT to by the PCT which contains in P1.3 PDWN its address registers the individual MSM XT 9831 4.096MHz ROM addresses of words which XT are part of a desired sentence. GND Upon selection of either of the addresses, a complete sentence FIGURE 3. Typical application with ceramic oscillator. can be replayed without need for picking every word one by one Note that this stop timing varies from the ROM. As illustrated in the block proportionally with the sampling diagram, the PCT reduces the frequency. ROM area by 2KBit, however,
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Item ROM Size Playback Time * Phrases Operating Modes MCU Control Phrase Control Oscillation Active current Packaging
MSM9831 384KBit 11.8 sec 31 MCU serial yes 4.096MHz 8mA 8-SOP
MSM9802 512KBit 16 sec 56/63 SA/MCU parallel yes
256kHz/ 4.096MHz
MSM9803 1MBit 32.4 sec 56/63 SA/MCU parallel yes
256kHz/ 4.096MHz
MSM9805 2MBit 65.1 sec 56/63 SA/MCU parallel yes
256kHz/ 4.096MHz
MSM98P05 2MBit OTP 65.1 sec 56/63 SA/MCU parallel yes
256kHz/ 4.096MHz
MSM9836 3MBit 98 sec 127 MCU parallel yes
4.096MHz
Code Development
Speech or sound codes are generated with a development system from OKI for the PC, designated the AR204. It consists of a 16-Bit ISA card, Windows 95(R) software and a ROM programming unit (Photo 1).
16mA
18-DIP, 24-SOP, 30-SSOP
16mA
18-DIP, 24-SOP, 30-SSOP
16mA
18-DIP, 24-SOP, 30-SSOP
16mA 20-DIP, 24-SOP
16mA 24-SOP
TABLE 3. MSM9800 series of non-linear PCM speech playback LSIs with internal mask ROM. * Playback times are given for 4kHz sampling frequency.-
Product Line-Up
MSM9831 is the smallest in a series of non-linear PCM speech synthesisers from OKI. MSM9836, MSM9805, MSM9803 and MSM9802 provide 3, 2, 1 and 0.5MBit internal ROM, respectively and allow for up to 63 or 127 playback channels. In principle, the MSM9831 is a downsized version of the MSM9802 with less ROM, less playback channels, simplified control interface, smaller package and lower cost.
Application Products
Typical applications for the MSM9831 are primarily in the field of consumer and AV goods, but not exclusively. For example:
PHOTO 1. The AR204 development system's working screen.

Automotive Telephones, Handies Facsimilie Peripheral Equipment Security Systems Digital Still Cameras Digital Video Cameras Household Appliances Clocks Toys, etc.
Aided by this system, the user can record voice and edit it so as to best suit his needs. ROM address and PCT address allocations can be assigned easily by the AR204 software. It also performs selection of oscillator mode, playback of individual ROM phrases and PCT playback simulation. The so developed data is converted to a HEX file and programmed into an EPROM. That EPROM will then contain the data with which OKI will produce the mask for the MSM9831 and other devices in the series.
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Oscillator
In particular, SMD type crystal oscillators exhibit narrow tolerances for stable startup and continuous oscillation. Once oscillation fails, the entire circuit will size operation like a vehicle without fuel. Oscillation margin is the capability of a circuit to activate and keep oscillation going on reliably. It is therefore important to determine which crystal impedance value is tolerated by its hosting circuit in its designated operating environment. This can be facilitated in the following manner:
2. How to: 2-1 Set RV to its minimum value and check whether normal oscillation sets in. 2-2 Set RV to maximum value to stop oscillation. If oscillation
2-5 Measure the current value of RV and record it as for instance RVX. 2-6 Calculate +R as RVX + RO Pictured in Figure 6 are typical examples for measuring circuits showing direct pick up and inductive pick-up in conjunction with a frequency counter. To accurate measure oscillation, the use of a frequency counter is useful, since spectrum analysers are not designed to distinguish main oscillation and spurious mode. A start-up detector should be used and connected where it will least affect circuit characteristics.
FIGURE 6. Recommended measuring circuit.
1. First of all: 1-1 For best results, use a crystal with known RO 1-2 For RV, use a precision potentiometer with maximum resistances of 1, 2, 5 or 10k, while 5k is a commonly used value.
still does not stop use a RV with larger maximum resistance value. 2-3 From this no-oscillation state reduce RV gradually until oscillation starts. 2-4 For maximum safety, repeat 2-1 to 2-3.
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Important Notice
OKI does not assume any responsibility for the consequences of improper handling or operation and shall neither be liable for any use or application. The customer acts on his own responsibility and shall himself make sure not to infringe any third party rights in using the product. Certain products described herein fall within the category of strategic goods, etc. under Foreign Trade Control Law. Accordingly, before exporting such products, you are required to file an application for export licence with your Government authorities. For product availability details, please be so kind as to contact your nearest OKI representative. The information in this brochure merely contains a general product description. If you require all about a product of interest, please be so kind as to ask for its latest data sheet. Specifications are subject to change without notice. This issue substitutes and supersedes all semiconductor shortform catalogues previously supplied by OKI. All brand, company and product names are the trademarks or registered trademarks of their respective owners.
People To People Technology
OKI Electric Industry Co., Ltd., Device Business Group, 10-3, Shibaura, 4-chome, Minato-ku, Tokyo 108, Japan, Tel.: +81-(0)3-5445-6327, Fax.: +81-(0)3-5445-6328, http://www.oki.co.jp/ OKI Semiconductor Group, 785 North Mary Avenue, Sunnyvale, CA 94086, U.S.A., Tel.: +1-408-720-1900, Fax.: +1-408-720-1918, http://www.okisemi.com/ OKI Electric Europe GmbH, Head Office Europe, Hellersbergstrasse 2, D-41460 Neuss, Germany, Tel: +49-2131-15960, Fax: +49-2131-103539, http://www.oki-europe.de/ OKI Electronics (Hong Kong) Ltd., Suite 1901-1&19, Tower 3, China Hong Kong City, 33 Canton Road, Tsimshatsui, Kowloon, Hong Kong, Tel.: +852-2-736-2336, Fax.: +852-2-736-2395 OKI Semiconductor (Asia) Pte. Ltd., 78 Shenton Way 09-01, Singapore 0207, Tel.: +65-221-3722, Fax.: +65-323-5376 OKI Semiconductor (Asia) Pte. Ltd., Taipei Branch, 7th Fl. No.260, Tun Hwa North Road, Taipei, Taiwan, R.O.C., Sumitomo-Flysun Building, Tel.: +886-2-2719-2561, Fax.: +886-2-2715-2892 http://www.oki.net.tw/
Copyright 1998 OKI. Ref.: MSM9831APP 3*98RB
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