71M6521BE
Energy Meter IC
DATA SHEET
JANUARY 2008
Internal Data Memory: The lower 128 bytes contain working registers and bit-addressable memory. The lower 32 bytes form
four banks of eight registers (R0-R7). Two bits on the program memory status word (PSW) select which bank is in use. The
next 16 bytes form a block of bit-addressable memory space at bit addressees 0x00-0x7F. All of the bytes in the lower 128
bytes are accessible through direct or indirect addressing. Table 5 shows the internal data memory map.
Address
0xFF
0x80
Direct addressing
Indirect addressing
RAM
Special Function Registers
(SFRs)
0x7F
0x30
Byte-addressable area
0x2F
0x20
Bit-addressable area
0x1F
0x00
Register banks R0…R7
Table 5: Internal Data Memory Map
Special Function Registers (SFRs)
A map of the Special Function Registers is shown in Table 6.
Bit-address-
Byte-addressable
able
Hex\Bin
Bin/Hex
X000
INTBITS
B
X001
X010
X011
X100
X101
X110
X111
F8
F0
E8
E0
D8
FF
F7
EF
E7
DF
WDI
A
WDCON
PSW
D0
D7
T2CON
IRCON
IEN1
C8
C0
B8
B0
A8
A0
98
90
88
80
CF
C7
BF
B7
AF
A7
9F
97
IP1
S0RELH
FLSHCTL
S0RELL
DIR0
S1RELH
S1CON
USR2
PGADR
IEN0
P2
IP0
DIR2
S0BUF
DIR1
TMOD
SP
S0CON
P1
IEN2
S1BUF
ERASE
TH0
S1RELL EEDATA EECTRL
DPS
TCON
P0
TL0
TL1
TH1
CKCON
8F
87
DPL
DPH
DPL1
DPH1
WDTREL
PCON
Table 6: Special Function Registers Locations
Only a few addresses are occupied, the others are not implemented. SFRs specific to the 6521BE are shown in bold print. Any
read access to unimplemented addresses will return undefined data, while any write access will have no effect. The registers at
0x80, 0x88, 0x90, etc., are bit-addressable, all others are byte-addressable.
Page: 18 of 97
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