Intel 80C186XL, 80C188XL user manual Convert Byte to Word, Clear Carry flag, Clear Direction flag

INSTRUCTION SET DESCRIPTIONS

Table C-4. Instruction Set (Continued)

Name	Description		Operation	Flags
				Affected
CBW	Convert Byte to Word:	if		AF –
	CBW	(AL) < 80H		CF –
		then		DF –
	Extends the sign of the byte in register
		(AH) ← 0		IF –
	AL throughout register AH. Use to
		else		OF –
	produce a double-length (word)
		(AH) ← FFH		PF –
	dividend from a byte prior to
				SF –
	performing byte division.
				TF –
	Instruction Operands:
				ZF –
	none
CLC	Clear Carry flag:	(CF) ← 0		AF –
	CLC			CF ¸
	Zeroes the carry flag (CF) and affects			DF –
				IF –
	no other flags. Useful in conjunction
				OF –
	with the rotate through carry left (RCL)
				PF –
	and the rotate through carry right
				SF –
	(RCR) instructions.
				TF –
	Instruction Operands:
				ZF –
	none
CLD	Clear Direction flag:	(DF) ← 0		AF –
	CLD			CF –
				DF ¸
	Zeroes the direction flag (DF) causing
				IF –
	the string instructions to auto-
				OF –
	increment the source index (SI) and/or
				PF –
	destination index (DI) registers.
				SF –
	Instruction Operands:
				TF –
	none			ZF –

NOTE: The three symbols used in the Flags Affected column are defined as follows:

–the contents of the flag remain unchanged after the instruction is executed ¸? the contents of the flag is undefined after the instruction is executed

the flag is updated after the instruction is executed

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