SPO256

Overview

The SPO256 is a speech synthesizer IC containing a 2Kx8-bit ROM, a clock oscillator, control logic, a digital filter and a pulse width modulator. It has a vocabulary of 64 allophones or basic speech sounds, allowing the user to join these together to give a reasonable representation of any English word.

Pinouts

             +----+--+----+
        GND -+  1 |__| 28 +- Osc 2
      _____  |            |
      RESET -+            +- Osc 1
             |            |
ROM disable -+            +- ROM Clock
             |            |  _________
         C1 -+            +- SBY Reset
             |            |
         C2 -+            +- Digital out
             |            |
         C3 -+            +- Vd1
             |            |
        +5V -+            +- Test
             |            |
        SBY -+            +- Ser in
        ___  |            |  ___
        LRQ -+            +- ALD
             |            |
         A8 -+            +- SE
             |            |
         A7 -+            +- A1
             |            |
    Ser out -+            +- A2
             |            |
         A6 -+            +- A3
             |            |
         A5 -+ 14      15 +- A4
             +------------+

There are eight address inputs (A1-A8), but A7 and A8 are not normally used and are tied to GND. The lower six address inputs are used to select the required allophone. It is recommended that the IC is driven from a latching parallel port.

Operation

ALD is an input that is used to trigger the device - this requires a brief negative pulse. The status output LRQ must then be monitored until it indicates completion of the allophone by going low.

The digital output at pin 24 is in fact the audio output but is in the form of a pulse-width-modulated digital signal. In order to recover the audio frequency output signal, it is necessary to use a low-pass filter with a cut-off frequency of 5KHz to eliminate the carrier.

Allophones

The IC provides five pauses as part of its set of allophones - these are useful for providing gaps between words without having to use software timing loops. The best approach for intelligible speech is to think about how the word or phrase is spoken and then to experiment with the relevant allophones and pauses. In the list below, the allophone consists of the letter(s) in capitals.

Address		Allophone		Address		Allophone

 0		10ms pause		32		OUt
 1		30ms pause		33		DOg
 2		50ms pause		34		pIG
 3		100ms pause		35		Vest
 4		200ms pause		36		GUest
 5		tOY			37		SHine
 6		flY			38		aZure
 7		End			39		bRave
 8		Come			40		Find
 9		Power			41		sKy
10		dodGe			42		Camera
11		biN			43		Zoo
12		pIn			44		raNG
13		To			45		Light
14		Ran			46		Win
15		sUcceed			47		repaiR
16		Man			48		WHen
17		carT			49		Yet
18		THey			50		CHair
19		sEE			51		tURn
20		bAy			52		cERtain
21		coulD			53		tOW
22		dO			54		THere
23		cAUght			55		beSt
24		tOp			56		Now
25		YEt			57		Home
26		bAt			58		stORe
27		Hat			59		bARn
28		Ban			60		cleAR
29		THin			61		Gone
30		lOOk			62		saddLe
31		fOOd			63		draB

Applications

The SPO256 has been used in the Currah uSpeech unit for the ZX Spectrum and also in the speech add-on module for the Mattel Intellivision. At the time of writing (January 1995), it appears difficult, if not impossible to obtain the IC and will therefore only be of interest to owners of the aforementioned equipment.

References

Micro Interfacing Circuits - Book 2, by R. A. Penfold, ISBN 0-85934-106-2.

This text was created by Alastair Booker on 17th-23rd January 1995 and finally converted into HTML on 22nd February 2000. Please feel free to contact me regarding anything mentioned here. Note that I am not very familiar with this IC any more.