To perform BCD arithmetic, MCS-51 off ers DA A instruction. Execution of this instruction needs some
prerequisites. To start with, DA A may only be used immediately after executing either ADD or ADDC
instruction of any addressing mode. DA A would be of no use even after a SUBB instruction. Loading any
number in the accumulator and then executing DA A instruction would not change the accumulator contents
to its BCD equivalent (refer to Fig. 12.13).
Figure 12.14Execution of DA A instruction
Instruction: DA A
Bytes: 1
Cycles: 1
CY
PSW
0202
020331
30
2F
0C
0B
0A
09
08
07
06
05
04
03
02
01
00
0201
0200
01FF
01FE
Reg. A
Reg. B
NOTE: See text for ...
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