SUBCY sX, Operand —Subtract Operand from Register sX with Borrow

R

Description

Operand and CARRY flag are subtracted from register sX. The ZERO and CARRY flags are set appropriately.

Pseudocode

if (CARRY = 1) then

sX Å (sX - Operand – 1) mod 256; always an 8-bit result

else

 

sX Å (sX – Operand) mod 256

; always an 8-bit result

endif

 

if ( (sX - Operand – CARRY) < 0 ) then

CARRY Å 1 else

CARRY Å 0 endif

if ( ((sX - Operand - CARRY) = 0) or ((sX - Operand - CARRY) = -256) ) then

ZERO Å 1 else

ZERO Å 0 endif

PC Å PC + 1

Registers/Flags Altered

Registers: sX

Flags: CARRY, ZERO

Notes

pBlazIDE Equivalent: SUBC

PicoBlaze 8-bit Embedded Microcontroller

www.xilinx.com

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UG129 (v1.1.2) June 24, 2008

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Image 115
Xilinx UG129 manual Registers sX Flags CARRY, Zero PBlazIDE Equivalent Subc