71M6511/71M6511H
Single-Phase Energy Meter IC
DATA SHEET
AUGUST 2007
Accumulator (ACC, A): ACC is the accumulator register. Most instructions use the accumulator to hold the operand. The
mnemonics for accumulator-specific instructions refer to accumulator as “A”, not ACC.
B Register: The B register is used during multiply and divide instructions. It can also be used as a scratch-pad register to hold
temporary data.
Program Status Word (PSW):
MSB
LSB
CV
AC
F0
RS1
RS
OV
-
P
Table 9: PSW Register Flags
Bit
Symbol
Function
Carry flag
Auxiliary Carry flag for BCD operations
PSW.7
PSW.6
PSW.5
CV
AC
F0
General purpose Flag 0 available for user. Not to be confused with the F0 flag
in the CE STATUS register.
PSW.4
RS1
Register bank select control bits. The contents of RS1 and RS0 select the working
register bank:
RS1/RS0
Bank selected
Location
00
01
10
11
Bank 0
Bank 1
Bank 2
Bank 3
(0x00 – 0x07)
(0x08 – 0x0F)
(0x10 – 0x17)
(0x18 – 0x1F)
PSW.3
RS0
PSW.2
PSW.1
PSW.0
OV
-
P
Overflow flag
User defined flag
Parity flag, affected by hardware to indicate odd / even number of “one” bits in the
Accumulator, i.e. even parity.
Table 10: PSW bit functions
Stack Pointer (SP): The stack pointer is a 1-byte register initialized to 0x07 after reset. This register is incremented before
PUSH and CALL instructions, causing the stack to begin at location 0x08.
Data Pointer: The data pointer (DPTR) is 2 bytes wide. The lower part is DPL, and the highest is DPH. It can be loaded as a
2-byte register (MOV DPTR,#data16) or as two registers (e.g. MOV DPL,#data8). It is generally used to access external code
or data space (e.g. MOVC A,@A+DPTR or MOVX A,@DPTR respectively).
Program Counter: The program counter (PC) is 2 bytes wide initialized to 0x0000 after reset. This register is incremented
during the fetching operation code or when operating on data from program memory.
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