PM0044 datasheet(95/162 Pages) STMICROELECTRONICS

95 / 162 page

PM0044

STM8 instruction set

Doc ID 13590 Rev 3

95/162

Syntax

CPW dst,src

e.g. CPW Y,(tbl,X)

Operation

{N, Z, C} = Test (dst - src)

Description

The source byte is subtracted from the destination byte and the result is

lost. However, N, Z, C flags of Condition Code (CC) register are updated

according to the result. The destination is an index register, and the source

is a memory or data word. This instruction generally is used just before a

conditional jump instruction.

Instruction overview

⇒

(X15.M15 + X15.R15 + X15.M15.R15)

⊕ (X14.M14 + X14.R14 + X14.M14.R14)

Set if the signed subtraction of the destination (dst) value from the source (src)

value generates a signed overflow (signed result cannot be represented on 16

bits).

⇒

R15

Set if bit 7 of the result is set (negative value), cleared otherwise.

⇒

R15.R14.R13.R12.R11.R10.R9.R8.R7.R6.R5.R4.R3.R2.R1.R0

Set if the result is zero (0x00), cleared otherwise.

⇒

(X15.M15 + X15.R15 + X15.M15.R15)

Set if the unsigned value of the contents of source (src) is larger than the

unsigned value of the destination (dst), cleared otherwise.

Detailed description

CPW

Compare word

CPW

mnem

dst

src

Affected condition flags

VI1

CPW

Reg

Mem

---

dst

src

Asm

lgth

Op-code(s)

ST7

#word

CPW X,#$10

A3 MS LS

✗

shortmem

CPW X,$10

✗

longmem

CPW X,$1000

C3 MS LS

✗

X(Y)

CPW X,(Y)

✗

(shortoff,Y)

CPW X,($10,Y)

✗

(longoff,Y)

CPW X,($1000,Y)

D3 MS LS

✗

(shortoff,SP)

CPW X,($10,SP)

[shortptr.w]

CPW X,[$10.w]

✗

[longptr.w]

CPW X,[$1000.w]

C3 MS LS

([shortptr.w],Y)

CPW X,([$10.w],Y)

✗

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