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Individual Instruction Descriptions
4-178
4.14.81 SUBB Subtract Byte
Syntax
[label] name dest, src Clock, clk Word, w With RPT, clk Class
SUBB An, imm8 1 1 N/R 2a
SUBB Rx, imm8 1 1 N/R 4b
Execution dest ⇐ dest – imm8
PC ⇐ PC + 1
Flags Affected dest is An: OF, SF, ZF, CF are set accordingly
dest is Rx: RCF, RZF are set accordingly
Opcode
Instructions 16 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0
SUBB An imm8 1 0 1 0 0 1 0 An imm8
SUBB Rx, imm8 1 0 1 1 0 1 k4 k3 k2 k7 k6 k5 Rx k1 k0
Description Subtract value of src byte from value of dest byte and store result in dest. Note
that subtraction is performed in 2’s complement and therefore the CF (carry
flag) may get set even when subtracting a smaller value from a larger value.
Syntax Description
SUBB An, imm8 Subtract immediate byte from An
SUBB Rx, imm8 Subtract immediate byte from Rx
Example 4.14.81.1 SUBB A2, 0x45
Subtract 0x45 from accumulator A2 byte.
Example 4.14.81.2 SUBB R3, 0xF2
Subtract 0xF2 from register R3 byte.