UPSD3212C, UPSD3212CV
SFR
Addressing Modes
The SFRs can only be addressed directly in the
address range from 80h to FFh. Table 15, page 32
gives an overview of the Special Function Regis-
ters. Sixteen address in the SFRs space are both-
byte and bit-addressable. The bit-addressable
SFRs are those whose address ends in 0h and 8h.
The bit addresses in this area are 80h to FFh.
The addressing modes in uPSD321X Devices in-
struction set are as follows
■ Direct addressing
■ Indirect addressing
■ Register addressing
■ Register-specific addressing
■ Immediate constants addressing
■ Indexed addressing
Table 3. RAM Address
Byte Address
(in Hexadecimal)
Byte Address
(in Decimal)
(1) Direct addressing. In a direct addressing the
operand is specified by an 8-bit address field in the
instruction. Only internal Data RAM and SFRs
(80~FFH RAM) can be directly addressed.
↓
↓
255
48
FFh
30h
msb
Example:
Bit Address (Hex)
lsb
mov A, 3EH ;A <----- RAM[3E]
2Fh 7F 7E 7D 7C 7B 7A 79 78 47
2Eh 77 76 75 74 73 72 71 70 46
2Dh 6F 6E 6D 6C 6B 6A 69 68 45
2Ch 67 66 65 64 63 62 61 60 44
2Bh 5F 5E 5D 5C 5B 5A 59 58 43
2Ah 57 56 55 54 53 52 51 50 42
29h 4F 4E 4D 4C 4B 4A 49 48 41
28h 47 46 45 44 43 42 41 40 40
27h 3F 3E 3D 3C 3B 3A 39 38 39
26h 37 36 35 34 33 32 31 30 38
25h 2F 2E 2D 2C 2B 2A 29 28 37
24h 27 26 25 24 23 22 21 20 36
23h 1F 1E 1D 1C 1B 1A 19 18 35
22h 17 16 15 14 13 12 11 10 34
21h 0F 0E 0D 0C 0B 0A 09 08 33
20h 07 06 05 04 03 02 01 00 32
Figure 11. Direct Addressing
Program Memory
A
3Eh
04
AI06641
(2) Indirect addressing. In indirect addressing
the instruction specifies a register which contains
the address of the operand. Both internal and ex-
ternal RAM can be indirectly addressed. The ad-
dress register for 8-bit addresses can be R0 or R1
of the selected register bank, or the Stack Pointer.
The address register for 16-bit addresses can only
be the 16-bit “data pointer” register, DPTR.
Example:
mov @R1, #40 H ;[R1] <-----40H
1Fh
18h
17h
10h
0Fh
08h
07h
00h
31
24
23
16
15
8
Register Bank 3
Register Bank 2
Register Bank 1
Register Bank 0
Figure 12. Indirect Addressing
Program Memory
55h
R1
40h
55
7
0
AI06642
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