The SSB-MPF used the TMS5200 or TMS5220 VSP (Voice Synthesis Processor) chip for speech synthesis based on LPC (Linear Predictive Coding) technology, pioneered by Texas Instruments. There were two ways the VSP chip could be fed speech-data, with a special VSM (Voice Synthesis Memory) chip, connected to a dedicated interface on the VSP, or by the CPU feeding it over the regular data bus.

The original VSM is the TMS6100, which has a capacity of 128kbit (16kByte). The TSM6125 was a smaller size in both capacity 32kbit (4kByte) as physical size. These chips were masked programmed at the factory for a special product.

The VSP and VSM were not regular 5 volt integrated circuits, but actual required 10 volt, usually configured as +/- 5 volt. The CPU interface was TTL-compatible. Data from the VSM was addressed by feeding five nibbles (4-bits each) over the ADD-bus, and then serially send over the ADD8 line to the VSP. Several VSMs could be connected to the VSP simultaneously.

These are the commands the TSM 5200 accepts. The SSB-MPF routines only uses only "Reset" and "Speak External".

Operation

Data bus command code
X000XXXX	Nop
X001XXXX	Read Byte
X010XXXX	Nop
X110XXXX	Speak External (data from CPU)
X011XXXX	Read and Branch
X100AAAA*	Load Address
X101XXXX	Speak (data from VSM)
X111XXXX	Reset

The basic SSB-MPF comes with a single ROM at 5000H containing a speaking clock demo program (5000H), an isolated routine to have the TMS 5200 say a word from a SSB-ROM (5200h), and a list of 36 words used by the clock demo. The manual lists the words for an additional eight ROMS, to be purchased seperately. The words are sorted alphabetically, so you probably had to buy all of them and compile your own sub set, as there is no room for all ROMs.

The ROM data is copied to the VSP verbatim, leaving the sorting of the variable data length to the VSP. It is also the VSP that signals the CPU that all the data for the current word is sent.

Because not everone has an operational TMS5200 system, I made a recording of the words in the standard U5 ROM. The program to speak them is 308 bytes. I didn't type all those bytes, but used a ROM emulator:

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More on the ROM emulator.

Local links:

• Speaking clock demo
• Speak a word from ROM demo
• Program that speaks all words from the U5 ROM
• Recording of the 'speakBasicWords' program

Interesting links:

• information on TI Speech & Spell modules including the actual chips inside the different versions.
• Wikipedia on the TMS6100
• Texas Instruments LPC Speech Chips
• an Arduino implementation of the Texas Instruments speech synthesis architecture
• BlueWizard, an Objective-C re-implementation of the Qboxpro LPC analyser

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Last update: 2020-09-06