An Ultimate RISC Processor for Space Applications Eli

An Ultimate RISC Processor for Space Applications Eli Kane Mesa State College, Grand Junction, CO 81501

Size and Power ● Aerospace devices are typically crowded ● Power available for devices is limited ● Embedded devices must meet tight space and power restrictions

Advantages of Ultimate Minimal RISC ● Very low gate count required ● Larger gate-size devices can be used, improving SEU resistance ● Physically smaller device can be used, saving PCB space ● ● ● High density devices can contain more processors per unit die area for parallel applications Reduced propagation delays in processor can help meet timing constraints Small size can allow programmability in applications where it is currently missing

What is an Ultimate RISC? ● ● ● Single instruction computer Subtract memory from memory and branch if negative Move memory to memory, if ALU and accumulator are mapped to memory

SUBNE ● Subtract memory from memory, branch on negative Example: Add two numbers a and b subnetmp, +1 subnetmp, b, +2 subnea, tmp, +1. . . ; set to 0 ; test if b is positive ; b was negative, ; b was positive, so sub -b

Move Memory to Memory ● Move Machine ● PC, ALU, and Accumulator memory mapped ● To perform calculations, write to ALU functions ● To branch, write to PC

Really Simple Processor ● Move Machine (currently an 8/16 bit processor) ● 6 registers and ALU memory mapped ● ● ● PC, other registers, ALU occupy upper 16 words, 0 xf 0 -0 xff Data, scratch pad, other uses occupy next upper words, 0 xe 0 -0 xef Code starts at 0 x 00 and extends upward

Registers in RSP ● PC - the program counter ● SRC - source address loaded here ● DST - destination address loaded here ● TMP - used to transfer data from SRC to DST ● Accumulator – stores ALU results ● Flags – stores flags such as Zero and Carry

Execution Unit

ALU