S1C63656 TECHNICAL MANUAL
EPSON
105
CHAPTER 4: PERIPHERAL CIRCUITS AND OPERATION (Integer Multiplier)
4.13.4 Execution cycle
Both the multiplication and division take 10 CPU cycles for an operation. Therefore, before the results can
be read from the destination register DRH/DRL, wait at least 5 bus cycles after writing to CALMD. The
same applies to reading the operation flags NF/VF/ZF.
The following shows a sample program.
ldb
%ext, src_data@h
ldb
%xl, src_data@l
; Set RAM address for operand
ldb
%ext, au@h
ldb
%yl, au@l
; Set multiplier I/O memory address
;
ldb
%ba, [%x]+
ldb
[%y]+, %ba
; Set data to SR
ldb
%ba, [%x]+
ldb
[%y]+, %ba
; Set data to DRL
ldb
%ba, [%x]+
ldb
[%y]+, %ba
; Set data to DRH
;
ld
[%y], 0b0001
; Start operation (select calculation mode)
;
ldb
%ext, rslt_data@h
ldb
%xl, rslt_data@l
; Set result store address
nop
nop
nop
; Dummy instructions to wait end of operation
;
bit
[%y], 0b0100
jrnz overflow
; Jump to error routine if VF = "1"
;
add
%y, -4
; Set DRL again
;
ldb
%ba, [%y]+
ldb
[%x]+, %ba
; Store result (quotient) into RAM
ldb
%ba, [%y]+
ldb
[%x]+, %ba
; Store result (remainder) into RAM