3.DETAILS ON RABBIT MICROPROCESSOR FEATURES

3.1Processor Registers

The Rabbit’s registers are nearly identical to those of the Z180 or the Z80. The figure below shows the register layout. The XPC and IP registers are new. The EIR register is the same as the Z80 I register, and is used to point to a table of interrupt vectors for the exter- nally generated interrupts. The IIR register occupies the same logical position in the instruction set as the Z80 R register, but its function is to point to an interrupt vector table for internally generated interrupts.

A

F

 

 

 

 

H

L

8/16-bit

 

 

D

E

registers

 

 

 

B

C

 

 

 

 

A'

F '

 

 

 

 

H '

L'

 

 

 

 

D '

E '

 

 

 

 

B '

C '

 

Alternate Registers

S Z x x x V x C

F - flag register layout

S-sign, Z-zero, V-overflow, C-carry Bits marked "x" are read/write.

IX

 

 

IP

 

 

 

 

 

 

 

IY

 

 

 

 

 

 

 

 

 

 

SP

 

 

IIR

 

 

 

 

 

 

 

PC

 

 

 

 

 

 

 

 

 

 

 

 

 

EIR

 

 

 

XPC

 

 

 

 

 

 

 

 

A- 8-bit accumulator

 

 

F - flags register

 

 

HL- 16-bit accumulator

 

 

IX, IY - Index registers/alt accum’s

 

 

SP - stack pointer

 

 

PC- program counter

 

 

XPC - extension of program counter

 

 

IIR - internal interrupt register

 

 

EIR-external interrupt register

 

 

IP - interrupt priority register

Figure 3-1. Rabbit Registers

User’s Manual

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Jameco Electronics 3000, 2000 manual Details on Rabbit Microprocessor Features, Processor Registers