UPI-41A/41AH/42/42AH USER’S MANUAL
DA A
Decimal Adjust Accumulator
Opcode:
0 1 0 1
0 1 1 1
The 8-bit accumulator value is adjusted to form two 4-bit Binary Coded Decimal (BCD) digits
following the binary addition of BCD numbers. The carry bit C is affected. If the contents of
bits 0 – 3 are greater than nine, or if AC is one, the accumulator is incremented by six.
The four high-order bits are then checked. If bits 4 – 7 exceed nine, or if C is one, these bits are
increased by six. If an overflow occurs, C is set to one; otherwise, it is cleared to zero.
Example:
Assume accumulator contains 9AH.
DA A
;ACC ADJUSTED TO 01H with C set
C
AC
ACC
0
0
9AH
INITIAL CONTENTS
06H
ADD SIX TO LOW DIGIT
0
0
A1H
60H
ADD SIX TO HIGH DIGIT
1
0
01H
RESULT
DEC A
Decrement Accumulator
Opcode:
0 0 0 0
0 1 1 1
The contents of the accumulator are decremented by one.
(A)
w
(A)
b
1
Example:
Decrement contents of data memory location 63.
MOV R0,
Ý
3FH
;MOVE ‘3F’ HEX TO REG 0
MOV A,
@
R0
;MOVE CONTENTS OF LOCATION 63
;TO ACC
DEC A
;DECREMENT ACC
MOV
@
R0,A
;MOVE CONTENTS OF ACC TO
;LOCATION 63
DEC Rr
Decrement Register
Opcode:
1 1 0 0
1 r
2
r
1
r
0
The contents of working register ‘r’ are decremented by one.
(Rr)
w
(Rr)
b
1
r
e
0 – 7
Example:
DECR1: DEC R1
;DECREMENT ADDRESS REG 1
DIS I
Disable IBF Interrupt
Opcode:
0 0 0 1
0 1 0 1
The input Buffer Full interrupt is disabled. The interrupt sequence is not initiated by WR and
CS, however, an IBF interrupt request is latched and remains pending until an EN I (enable
IBF interrupt) instruction is executed.
Note:
The IBF flag is set and cleared independent of the IBF interrupt request so that handshaking
protocol can continue normally.
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Содержание UPI- 41A
Страница 1: ...October 1993 Microprocessor Peripherals UPI 41A 41AH 42 42AH User s Manual Order Number 231318 006 ...
Страница 4: ......
Страница 12: ...UPI 41A 41AH 42 42AH USER S MANUAL 231318 7 Figure 2 2 Pin Configuration 231318 8 Figure 2 3 Logic Symbol 8 ...
Страница 65: ...UPI 41A 41AH 42 42AH USER S MANUAL 231318 42 Figure 5 11 Distributed Processor System 61 ...