Intel 8080 - B4_Page_05

Example 1:
Rotate accumulator right six times.
ROTR6:
Example
2:
REPT
RRC
ENDM
6
Chapter 5. Macros
The following REPT directive generates the source code for a routine that fills a five-byte field with the character
stored in the accumulator:
Example
3:
PROGRAM CODE
LHLD
REPT
MOY
INX
ENDM
CNTR1
5
M,A
H
GENERA TED CODING
LHLD CNTR1
MOY
M,A
INX
H
MOY
M,A
INX
H
MOY
M,A
INX
H
MOY
M,A
INX
H
MOY
M,A
INX
H
The following example illustrates the
use of REPT to generate a multiplication routine. The multiplication is
accomplished through a series of shifts. If this technique is unfamiliar, refer to the example of multiplication
in Chapter 6. The example in Chapter 6 uses a program loop for the multiplication. This example replaces the
loop with seven repetitions of the four instructions enclosed by the REPT -ENDM directives.
Notice that the expansion specified
by this REPT directive causes the label SKIPAD to be generated seven times.
Therefore, SKIPAD must be declared local to this macro.
FSTMUL:
SKIPAD:
MYI
L.XI
REPT
LOCAL
RLC
INC
DAD
DAD
ENDM
RLC
RNC
D,O
H,O
7
SKIPAD
SKIPAD
D
H
DAD D
RET
;FAST MULTIPLY ROUTINE
;MULTIPLY E*A - 16-BIT RESULT
;IN H&L
;;GET NEXT MULTIPLIER BIT
;;DON'T ADD IF BIT =: °
;;ADD MULTIPLICAND INTO ANSWER
5-7