The Texas Instruments TMS7000 family supported, when produced and sold, very flexible configurations. The basic variant allowed for 2 or 4k Byte ROM and an option to include custom instructions the so called SCAT technology [1] ). This made the microcontroller interesting for cryptographic applications like early ATM-machines. The TMS7000 Family was produced and marketed in the late 1980s and 1990s. It was later rebranded as the TMS370 [2] .
Contents
Here a text from the TMS7000 Family Data Manual: [3]
The TMS7000 is a family of 8-bit single-chip microcontrollers. These microcontrollers incorporate a CPU, memory (ROM, RAM, EPROM), bit I/O, serial communications port, timers, interrupts, and external bus interface logic, all on a single chip. The CMOS members of the family provide an outstanding speed/power ratio as a result of the reliable silicon-gate CMOS technology.
In modern days manufacturer customization is no longer available as Texas Instruments no longer produces chips in this family. What remains is a quite advanced micro-controller, capable of read–modify–write instructions on all registers in the peripheral memory area. The chips have 128 or 256 bytes of internal memory, of which the first two locations are mapped to CPU-registers A and B. Effectively a 'zero page' with faster instructions. At the start of 'page one' are the Peripheral File registers for I/O-ports, timers and the serial port. The rest of this memory page is available for external devices, which profit from the faster instructions. Family members were produced in NMOS and CMOS technology.
Compared to other early microcontrollers like the Motorola MC6801/6803 which were based on the generic Motorola_6800_family microprocessor, the TMS7000 family has a specific microcontroller-oriented instruction set. This is visible in fast register-oriented instructions, which applied to the 'Peripheral File' memory page (0100-01FFh) containing the internal port control registers, timers, ... These instructions included the read-apply-logic-mask-write instructions (ANDP, ORP, XORP) and the read-apply-mask-and-jump (BTJOP, BTJZP,...).
Another special feature of the TMS7000 family is the micro-instruction format is published [4] . This allowed customers to create their own special instructions, which T.I. could integrate into custom versions of the die. This feature is the SCAT technology.
Over the time the TMS7000 family was marketed, it evolved the die technology (NMOS to CMOS), larger Register File memory 128 to 256 bytes), and optimized I/O registers. The latter meant the Peripheral File changed over time, making the binary code somewhat device-dependent. This could partly be mitigated by creating a device-specific Peripheral File mapping file.
The architecture could be operated in four port configurations, of which Single-Chip Mode and Microprocessor Mode are the extremes. In Single-Chip Mode only the internal ROM and RAM are used and all ports are available for I/O, in Microprocessor Mode the ports C and D are used for multiplexed data and address lines. Several lines of port A are then control lines (ALE, ENABLE, R/W) [5] .