HT47C20 Holtek Semiconductor Inc, HT47C20 Datasheet - Page 43

• Manufacturer Part Number: HT47C20
• Description: 8-Bit Microcontroller
• Manufacturer: Holtek Semiconductor Inc

CPLA [m]
Description
Operation
Affected flag(s)
DAA [m]
Description
Operation
Affected flag(s)
DEC [m]
Description
Operation
Affected flag(s)
Complement data memory-place result in accumulator
Each bit of the specified data memory is logically complemented (1 s
complement). Bits which previously contained a one are changed to zero
and vice-versa. The complemented result is stored in the accumulator
and the contents of the data memory remains unchanged.
ACC ¬ [m]
Decimal-Adjust accumulator for addition
The accumulator value is adjusted to the BCD(Binary Code Decimal)
code. The accumulator is divided into two nibbles. Each nibble is ad-
justed to the BCD code and an internal carry (AC1) will be done if the low
nibble of the accumulator is greater than 9. The BCD adjustment is done
by adding 6 to the original value if the original value is greater than 9 or
a carry (AC or C) is set; otherwise the original value remains unchanged.
The result is stored in the data memory and only the carry flag (C) may
be affected.
If (ACC.3~ACC.0) >9 or AC=1
then ([m].3~[m].0) ¬ (ACC.3~ACC.0)+6, AC1=AC
else ([m].3~[m].0) ¬ (ACC.3~ACC.0), AC1=0
If (ACC.7~ACC.4)+AC1 >9 or C=1
then ([m].7~[m].4) ¬ (ACC.7~ACC.4)+6+AC1, C=1
else ([m].7~[m].4) ¬ (ACC.7~ACC.4)+AC1, C=C
Decrement data memory
Data in the specified data memory is decremented by one.
[m] ¬ [m]-1
TC2
TC2
TC2
¾
¾
¾
TC1
TC1
TC1
¾
¾
¾
TO
TO
TO
¾
¾
¾
43
PD
PD
PD
¾
¾
¾
OV
OV
OV
¾
¾
¾
¾
Z
Ö
Z
Z
Ö
AC
AC
AC
¾
¾
¾
¾
¾
C
C
C
Ö
January 18, 2000
HT47C20