VRS51x550/560
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Program Memory
Program Memory
The VRS51x550 includes 8KB of on-chip Program
Flash
memory.
The
VRS51x560
includes
16KB
Program Flash memory.
FIGURE 3: VRS51X560 / VRS51X550 INTERNAL PROGRAM MEMORY
RM51x550
Flash Memory
(8K Bytes)
0000h
3FFFh
VRS51x560
Flash Memory
(16K Bytes)
0000h
1FFFh
Program Status Word Register
The PSW register is a bit addressable register that
contains the status flags (CY, AC, OV, P), user flag
(F0) and register bank select bits (RS1, RS0) of the
8051 processor.
TABLE 7: PROGRAM STATUS WORD REGISTER (PSW) - SFR DOH
7
6
5
4
3
2
1
0
CY
AC
F0
RS1
RS0
OV
-
P
Bit
Mnemonic
Description
7
CY
Carry Bit
6
AC
Auxiliary Carry Bit from bit 3 to 4.
5
F0
User definer flag
4
RS1
R0-R7 Registers bank select bit 0
3
RS0
R0-R7 Registers bank select bit 1
2
OV
Overflow flag
1
-
-
0
P
Parity flag
RS1
RS0
Active Bank
Address
0
0
0
00h-07h
0
1
1
08h-0Fh
1
0
2
10h-17h
1
1
3
18-1Fh
Data Pointer
The VRS51x550 and VRS51x560 each have one 16-bit
data pointer. The DPTR is accessed through two SFR
addresses: DPL located at address 82h and DPH
located at address 83h.
Data Memory
The VRS51x550 and VRS51x560 each have a total of:
256 bytes of RAM configured like the internal memory
structure of a standard 8052.
FIGURE 4: VRS51X550 /VRS51X560 RAM MEMORY OVERVIEW
Lower 128 bytes (00h to 7Fh, Bank 0 & Bank 1)
The lower 128 bytes of data memory (from 00h to 7Fh)
is summarized as follows:
• Address range 00h to 7Fh can be accessed in
direct and indirect addressing modes.
• Address range 00h to 1Fh includes R0-R7
registers area.
• Address range 20h to 2Fh is bit addressable.
• Address range 30h to 7Fh is not bit addressable
and can be used as general-purpose storage.
Upper 128 bytes (80h to FFh, Bank 2 & Bank 3)
The upper 128 bytes of data memory (from 80h to FFh)
can be accessed using indirect addressing or by using
the bank mapping in direct addressing mode.
FIGURE 5: VRS51X550 / VRS51X560 RAM STRUCTURE
Registers Bank 0
R7
-
R0
Registers Bank 1
R7
-
R0
Registers Bank 2
R7
-
R0
Registers Bank 3
R7
-
R0
80 Bytes of
General Purpose RAM
00h
08h
10h
18h
20h
07
06
05
04
03
02
01
00
0F
0E
0D
0C
0B
0A
09
08
77
76
75
74
73
72
71
70
7F
7E
7D
7C
7B
7A
79
78
30h
128 Bytes of
Indirect Access RAM
(SP, R0,R1)
80h
7Fh
FFh
2Fh
SFR Area
Direct or Bit Access
Only
FFh
85
84
83
82
81
80
P0
SP
DPL
DPH