Zilog Z8F0130 - Manual (Page 153)

eZ8
™
CPU Core
User Manual
UM012820-0810 DECW Instruction
138
Attributes
Escaped Mode Addressing
Using Escaped Mode Addressing, address modes RR can specify a work-
ing register Pair or IR can specify a working register. If the high nibble of
the source or destination address is
Eh ( 1110b ), a working register (or
Pair) is inferred. For example, if Working Register Pair R12 and R13
(with base address
Ch ) is the preferred destination operand, use ECh as the
destination operand in the Op Code. To access Register Pairs with
addresses
E0h to EFh , either set the Working Group Pointer, RP[7:4] , to
Eh or use indirect addressing.
Sample Usage
If Register Pair 30h and 31h contain the value 0AF2h , the following
statement leaves the value 0AF1h in Register Pair 30h and 31h and clears
the Z, V, and S flags:
DECW 30h

Object Code: 80 30
If Working Register R0 contains 30h and Register Pair 30h and 31h con-
tain the value FAF3h , the following statement leaves the value FAF2h in
Register Pair 30h and 31h , sets the S flag, and clears the. Z and V flags:
DECW @R0

Object Code: 81 E0
Mnemonic Destination
Op
Code
(Hex)
Operand 1 Operand 2 Operand 3
DECW RR1 80 RR1 — —
DECW @R1 81 R1 — —