Intel mcs-48 manual 10 CPU, Reset, Jump Test Condition Instructions Accumulator, Test Input-T1

SINGLE COMPONENT SYSTEM

PROG

	~			)Cf)C
DATA IN	V ADDRESSJ FLOAT
------		14 BITS)		(4 BITS)
DATA OUT	~ DATA
(P20·P23)	~ OUT
----- ....		(4 BITS)	'---~(4~BIT=S)~---------------
BITS 0,1		BITS 2,3
01OO} PORT	OO}READ
	01	WRITE
10 ADDRESS	10	OR
11	11	AND	PORT 2 FOR EXPANDED 1/0 WITH 8243

FIGURE 6. EXPANDED I/O TIMING DIAGRAM

2.10 CPU

The 8021 CPU has arithmetic and logical capability. A wide variety of arithmetic and logic instructions may be exercised, which affect the contents of the accumulator, and/or direct or indirect scratch pad loca- tions. Provisions have been made for simplified BCD arithmetic capability using the DAA, SWAP A, and XCHD instructions. In addition, MOVP A,@A allows table lookup for display formating and constants. The conditional branch logic within the processor enables several conditions inter- nal and external to the processor to be tested by the users program. Use the

conditional jump instructions with the tests listed below to effect a change in the program execution sequence.

	Jump	Jump
Test	Condition	Instructions
Accumulator	A=O A"'O	JZ JNZ
Carry Flag	o 1	,JC
Timer Overflow Flag	1	JTF
Test Input-T1	o 1	JNT1, JT1

2.11 Reset

Apositive-going signal to the RESET input resets the necessary miscellaneous flip- flops and sets "the program counter and stack pOinter to zero.

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