User’s Manual 13
3. DETAILS ON RABBIT
MICROPROCESSOR FEATURES
3.1 Processor 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.
Figure 3-1. Rabbit Registers
A
F
H
L
D
E
B
C
IX
IY
SP
PC
A '
F '
H '
L '
D '
E '
B '
C '
Alternate Registers
IP
XPC
IIR
EIR
F - flag register layout
SZ V C
S-sign, Z-zero, V-overflow, C-carry
xxx x
Bits marked "x" are read/write.
8 / 16 bit
registers
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
To Next Page
Loading...
