UPSD3212C, UPSD3212CV
First, pointers R1 and R0 are set up to point to the
two bytes containing the last four BCD digits. Then
a loop is executed which leaves the last byte, loca-
tion 2EH, holding the last two digits of the shifted
number. The pointers are decremented, and the
loop is repeated for location 2DH. The CJNE in-
struction (Compare and Jump if Not equal) is a
loop control that will be described later. The loop
executed from LOOP to CJNE for R1 = 2EH, 2DH,
2CH, and 2BH. At that point the digit that was orig-
inally shifted out on the right has propagated to lo-
cation 2AH. Since that location should be left with
0s, the lost digit is moved to the Accumulator.
Table 7. Shifting a BCD Number Two Digits to
the Right (using direct MOVs: 14 bytes)
2A 2B 2C 2D 2E ACC
MOV A,2Eh
00
12
12
12
12
00
34
34
34
12
12
56
56
34
34
34
78
56
56
56
56
78
78
78
78
78
MOV 2Eh,2Dh 00
MOV 2Dh,2Ch 00
MOV 2Ch,2Bh 00
MOV 2Bh,#0
00
Table 8. Shifting a BCD Number Two Digits to
the Right (using direct XCHs: 9 bytes)
2A 2B 2C 2D
2E ACC
CLR
A
00
00
00
00
00
12
00
00
00
00
34
34
12
12
12
56
56
56
34
34
78
78
78
78
56
00
12
34
56
78
XCH A,2Bh
XCH A,2Ch
XCH A,2Dh
XCH A,2Eh
Table 9. Shifting a BCD Number One Digit to the Right
2A
2B
12
12
2C
2D
56
56
2E
78
78
ACC
MOV
MOV
R1,#2Eh
R0,#2Dh
00
00
34
34
xx
xx
; loop for R1 = 2Eh
LOOP:
MOV
XCHD
SWAP
MOV
DEC
A,@R1
00
00
00
00
00
00
00
12
12
12
12
12
12
12
34
34
34
34
34
34
34
56
58
58
58
58
58
58
78
78
78
67
67
67
67
78
76
67
67
67
67
67
A,@R0
A
@R1,A
R1
DEC
R0
CNJE
R1,#2Ah,LOOP
; loop for R1 = 2Dh
; loop for R1 = 2Ch
; loop for R1 = 2Bh
00
00
08
12
18
01
38
23
23
45
45
45
67
67
67
45
23
01
CLR
XCH
A
08
00
01
01
23
23
45
45
67
67
00
08
A,2Ah
25/152
STMICROELECTRONICS [ ST ]
