AMI S2000
Developer	American Microsystems
Manufacturer	American Microsystems
Type	microcontrollers
Production	1977
Architecture	4-bit
ISA	S2000
Word size	4 bit 0.5 octets 1 nibbles
Technology	nMOS
Clock	0.9 MHz-3.6 MHz
Package	DIP 40, DIP28

The S2000 Family is a family of 4-bit microcontrollers developed by American Microsystems in mid 1977.

The chips came with 51/59 instructions - all single-cycle - operating at 4.5μs.

Members

MCU Family Members
Part	ROM	RAM	Notes
S2000	1k x 8-bit	64x 4-bit RAM	51 instructions, 0.9 MHz
S2000A	1k x 8-bit	64x 4-bit RAM	Identical to S2000 VFD driver support/high voltage support
S2150 S2152	1.5k x 8-bit	80x 4-bit RAM	51 instructions, 1.8 MHz
S2150A	1.5k x 8-bit	80x 4-bit RAM	Identical to S2150 VFD driver support/high voltage support
S2200	2k x 8-bit	128x 4-bit RAM	59 instructions, 3.6 MHz
S2200A	2k x 8-bit	128x 4-bit RAM	Identical to S2200 VFD driver support/high voltage support
S2400	4k x 8-bit	128x 4-bit RAM	59 instructions
S2400A	4k x 8-bit	128x 4-bit RAM	Identical to S2400 VFD driver support/high voltage support

Design

• S2000 is a family of 4-bit microcontrollers manufactured by American Microsystems, Inc (AMI) in the first half 1979. Depending on part number, 2000 or 2150, the microcontroller had either 32 or 40 byte on-chip scratchpad RAM, and 1 KB or 1.5 KB ROM. If desired, ROM memory could be extended to 8 KB by adding external ROM.

Instruction set of the MCU included 51 instructions, most of which occupied just one byte. Instruction set was rather simple, and included load and exchange operations, basic arithmetic instructions, I/O and control instructions. There was no conditional branch, but it was possible to simulate one by using conditional Skip instruction (which skipped the next instruction), followed by "Jump" instruction. While the S2000 microcontroller supported subroutines, due to small size of internal stack the subroutines were limited to three levels. The MCU didn't support interrupts.

The AMI S2000 MCUs were packaged into 40-pin plastic or ceramic DIP package. It was possible to order this part in 28-pin plastic and ceramic package - in this case the customer had to specify which optional pins could be removed from the package.

• S2200 is an enhanced version of AMI S2000 4-bit microcontroller. The S2200 has larger size of on-chip ROM, up to 4 KB ROM depending on part number, but the maximum external memory size stayed the same - 8 KB. On-chip RAM memory was expanded to 128 words, or 64 bytes.

The MCU has 12 new instructions and supports two-level interrupts. To accommodate interrupts, program counter stack was increased to 5 levels, and all other registers and a carry flag added separate 2-level interrupt stacks. These improvements were also useful for applications that didn't use interrupts, as the applications could nest subroutines to 5 levels rather than three. Whereas the S2000 MCU included 2 program controllable flags, that could be set, reset and tested by programs, the S2200 includes 262 of such flags. The S2200 microcontrollers has better programmable timer/counter, and add A/D and D/A converters. The S2200 MCU uses lower 5 Volt power supply. To further reduce power consumption, the parts could be ordered with RAM power-down option.

The AMI S2200 microcontrollers were packaged into 40-pin plastic or ceramic DIP package. Like on the S2200 microcontrollers, certain optional pins on the S2200 could be eliminated, and the MCU could be ordered in 28-pin plastic and ceramic package.

Documents

• S2000 Family Datasheet
• S2000 Family Programming Manual (1978)

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