TMS6100
The Texas Instruments TMS6100 is a 1 or 4-bit serial mask (factory)-programmed read-only memory IC. It is a companion chip to the TMS5100, CD2802, TMS5110, (rarely) TMS5200, and (rarely) TMS5220 speech synthesizer ICs, and was mask-programmed with LPC data required for a specific product. It holds 128Kib (16KiB) of data, and is mask-programmed with a start address for said data on a 16KiB boundary. It is also mask-programmable whether the /CE line needs to be high or low to activate, and also what the two (or four) 'internal' CE bits need to be set  to activate, effectively making the total addressable area 18 bits. Finally, it is mask-programmable whether the bits are read out 1-bit serially or 4 at a time. TMS6125. The "TMS6125" is a smaller, 32Kib (4KiB) version of effectively the same chip, with some minor changes to the 'address load' command format to reflect its smaller size. Texas Instruments calls both of these serial roms (TMS6100 and TMS6125) "VSM"s (Voice Synthesis Memory) on their datasheets and literature, and they will be referred to as such for the rest of this article. Both VSMs use 'local addressing', meaning the chip  keeps track of its own address pointer once loaded. Hence every bit in the chip can be sequentially read out, even though internally the chip stores data in 8-bit bytes. Commands. The VSM has supports 4 basic commands, based on two input pins called 'M0' and 'M1': Part Numbering. When used on Texas Instruments' Consumer Division products, the VSMs are always marked CDxxxxx where xxxxx is a 4 or 5 digit mask rom ID code, typically 23xx or 62xxx. The chips are SOMETIMES (typically after 1981) also marked TMC0350, as this seems to be the 'internal use class' of  the chip. The very first VSMs (used in the Speak and Spell, 1978 version) were marked TMC0351 and TMC0352 and did not have a CD number. These two SEEM to have been 'grandfathered in' as CD2300 and CD2301, as all later VSMs start at CD2302 (used in the 'Vowel Power' Speak and Spell expansion cartridge). It should also be noted that CD22xx, CD25xx and CD28xx numbers are used for chips that are NOT VSMs. When used on Texas Instruments' non-consumer division products (such as generic voice chips for other computers/measurement devices which were still TI-branded) the chips  are labeled VMxxxxx. When used on 3rd party products, the chips are marked CMxxxxx instead. The numbering scheme for the xxxxx part seems to be common between both CDxxxxx and CMxxxxx chips (but NOT VMxxxxx chips), so no chip of either series will have a common xxxxx number.