Table – ST & T UPSD3212C User Manual
Page 21
21/163
uPSD3212A, 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)
Table 8. Shifting a BCD Number Two Digits to
the Right (using direct XCHs: 9 bytes)
Table 9. Shifting a BCD Number One Digit to the Right
2A
2B
2C
2D
2E
ACC
MOV
A,2Eh
00
12
34
56
78
78
MOV
2Eh,2Dh
00
12
34
56
56
78
MOV
2Dh,2Ch
00
12
34
34
56
78
MOV
2Ch,2Bh
00
12
12
34
56
78
MOV
2Bh,#0
00
00
12
34
56
78
2A
2B
2C
2D
2E
ACC
CLR
A
00
12
34
56
78
00
XCH
A,2Bh
00
00
34
56
78
12
XCH
A,2Ch
00
00
12
56
78
34
XCH
A,2Dh
00
00
12
34
78
56
XCH
A,2Eh
00
00
12
34
56
78
2A
2B
2C
2D
2E
ACC
MOV
R1,#2Eh
00
12
34
56
78
xx
MOV
R0,#2Dh
00
12
34
56
78
xx
; loop for R1 = 2Eh
LOOP:
MOV
A,@R1
00
12
34
56
78
78
XCHD
A,@R0
00
12
34
58
78
76
SWAP
A
00
12
34
58
78
67
MOV
@R1,A
00
12
34
58
67
67
DEC
R1
00
12
34
58
67
67
DEC
R0
00
12
34
58
67
67
CNJE
R1,#2Ah,LOOP
00
12
34
58
67
67
; loop for R1 = 2Dh
00
12
38
45
67
45
; loop for R1 = 2Ch
00
18
23
45
67
23
; loop for R1 = 2Bh
08
01
23
45
67
01
CLR
A
08
01
23
45
67
00
XCH
A,2Ah
00
01
23
45
67
08