IOP16 Instructions Detail

IOP16 Instructions

• Details of the instructions follow
• Some instructions are psuedo-ops which are replaced with equivalent instructions
  • Used as convenience

Load Instruction

• Instruction to load register

LRI - Load Register with Immediate Value

• Load a register with an immediate value

Peripheral Load/Store Instructions

• Peripheral read/write instructions

IOR - I/O Read

• Read peripheral address into a register

IOW - I/O Write

• Write value from register to peripheral address

Shift/Rotate Instructions

• Shift/rotate instructions
• Logical/arithmetic operations
• The bottom 3-bits of the instruction have the count
  • Count is set to 1
  • Barrel shifter could be written to have other counts

SLL - Shift Logical Left

• Shift register left by 1
• Shifts in 0 to Least Significant bit

SLR - Shift Logical Right

• Shift register right by 1
• Shifts in 0 to Most Significant bit

SAL - Shift Arithmetic Left

• Shift register left by 1
• Shifts in 0 to Least Significant bit

SAR - Shift Arithmetic Right

• Shift register right by 1
• Shifts in 1 to Most Significant bit

RRL - Rotate Register Left

• Rotate Register left by 1
• Rotate Register MSB into Register Least Significant bit

RRR - Rotate Register Right

• Rotate register right by 1
• Rotate Register LSB into Register Most Significant bit

ALU Instruction

• Logical and Mathematical instructions

XRI - Exclusive-OR Register with Immediate Value

• Exclusive-OR Register with immediate value
• Store back into register

ORI - Logical OR Register with Immediate Value

• Logical OR Register with immediate value
• Store back into register

ARI - Logical AND Register with Immediate Value

• Logical AND Register with immediate value
• Store back into register

ADI - Add Register with Immediate Value

• Add Register with immediate value
• Store back into register

CMP - Compare Register with Immediate Value

• Compare register with Immediate value
• Set Conditional Code Register (CCR) bits

Flow Control Instructions

• Various instructions that can alter program flow
• Some are conditional branches, Bxx

RTS - Return from Subroutine

• Pops the program stack to use as a return address

JSR - Jump to Subroutine

• Push next address onto stack
• Jump to address

JMP - Jump

• Jump to address

BEZ - Branch if Equal to Zero

• If CCR Zero bit is set take branch

BNZ - Branch if Not Zero

• If CCR Zero bit is not set take branch

BEQ - Branch if Equal

• Psuedo-Instruction (same as BEZ)
• If CCR Equal bit is set take branch

BNE - Branch if Not Equal

• Psuedo-Instruction (Same as BNZ)
• If CCR Equal bit is clear take branch

Misc Instructions

NOP - No operation

• Psuedo-Instruction
• Coded as ORI Reg8,0x00

HALT

• Psuedo-Instruction performs branch to self

Instruction Encoding