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ML51/ML54/ML56
Sep. 01, 2020
Page
85
of 719
Rev 2.00
ML
51
/ML
54
/ML
5
6 S
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S
TECHNI
CA
L
RE
F
E
R
E
NC
E
M
A
NU
A
L
ML51/M
L54
/M
L56
Series
Tec
hnical Reference
Manual
Register Bank 0
Register Bank 1
Register Bank 2
Register Bank 3
03
02
01
00
04
05
06
07
0B
0A
09
08
0C
0D
0E
0F
13
12
11
10
14
15
16
17
1B
1A
19
18
1C
1D
1E
1F
23
22
21
20
24
25
26
27
2B
2A
29
28
2C
2D
2E
2F
33
32
31
30
34
35
36
37
3B
3A
39
38
3C
3D
3E
3F
43
42
41
40
44
45
46
47
4B
4A
49
48
4C
4D
4E
4F
53
52
51
50
54
55
56
57
5B
5A
59
58
5C
5D
5E
5F
63
62
61
60
64
65
66
67
6B
6A
69
68
6C
6D
6E
6F
73
72
71
70
74
75
76
77
7B
7A
79
78
7C
7D
7E
7F
Direct or Indirect Accessing RAM
Indirect Accessing RAM
00H
07H
28H
08H
0FH
10H
17H
18H
1FH
20H
21H
22H
23H
24H
25H
26H
27H
29H
2AH
2BH
2CH
2DH
2EH
2FH
30H
7FH
80H
FFH
00H
FFH
Bit-addressable
General Purpose Registers
General Purpose
Registers
Figure 6.1-4 Internal 256 Bytes RAM Addressing
On-Chip XRAM
6.1.5.2
The ML51/ML54/ML56 Series provides additional on-chip 4 Kbytes auxiliary RAM called XRAM to
enlarge the RAM space. It occupies the address space from 00H through FFH. The 4 Kbytes of XRAM
are indirectly accessed by move external instruction MOVX @DPTR or MOVX @Ri. (See the demo
code below.) Note that the stack pointer cannot be located in any part of XRAM.
XRAM demo code:
Assembler:
MOV R0,#23H
;write #5AH to XRAM with address @23H
MOV A,#5AH
MOVX @R0,A
MOV R1,#23H
;read from XRAM with address @23H
MOVX A,@R1
MOV DPTR,#0023H
;write #5BH to XRAM with address @0023H
MOV A,#5BH
MOVX @DPTR,A