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UM012811-0904
eZ8 CPU Instruction Set Description
eZ8 CPU
User Manual
97
CPX
Compare using Extended Addressing
CPX dst, src
Operation
dst - src
Description
The source operand is compared to (subtracted from) the destination operand and the
appropriate flags are set accordingly. The contents of both operands are unaffected.
Flags
Attributes
Escaped Mode Addressing
Using Escaped Mode Addressing, address mode ER for the source or destination can spec-
ify a Working Register with 4-bit addressing.
If the high byte of the source or destination address is EEH (11101110B), a Working Reg-
ister is inferred. For example, the operand EE3H selects Working Register R3. The full 12-
bit address is given by {RP[3:0], RP[7:4], 3H}.
To access Registers on Page EH (addresses E00H to EFFH), set the Page Pointer, RP[3:0],
to EH and set the Working Group Pointer, RP[7:4], to the desired Working Group.
C
Set if a borrow is required by bit 7; reset otherwise.
Z
Set if the result is zero; reset otherwise.
S
Set if the result is negative; reset otherwise.
V
Set if an arithmetic overflow occurs; reset otherwise.
D
Unaffected.
H
Unaffected.
Mnemonic Destination, Source
Opcode (Hex)
Operand 1
Operand 2
Operand 3
CPX
ER1, ER2
A8
ER2[11:4]
{ER2[3:0], ER1[11:8]} ER1[7:0]
CPX
ER1, IM
A9
IM
{0H, ER1[11:8]}
ER1[7:0]