71m6521fe Maxim Integrated Products, Inc., 71m6521fe Datasheet - Page 20

• Manufacturer Part Number: 71m6521fe
• Description: Energy Meter Ic
• Manufacturer: Maxim Integrated Products, Inc.

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):
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 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
when fetching operation code or when operating on data from program memory.
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PSW.7
PSW.6
PSW.5
PSW.4
PSW.3
PSW.2
PSW.1
PSW.0
Bit
MSB
CV
Symbol
RS1
RS0
OV
CV
AC
F0
P
-
AC
Function
Carry flag
Auxiliary Carry flag for BCD operations
General purpose Flag 0 available for user.
Register bank select control bits. The contents of RS1 and RS0 select the working
register bank:
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.
© 2005-2008 TERIDIAN Semiconductor Corporation
F0
F0 is not to be confused with the F0 flag in the CE STATUS register.
RS1/RS0
00
01
10
11
Table 9: PSW Register Flags
Table 10: PSW Bit Functions
RS1
Bank selected
RS
Bank 0
Bank 1
Bank 2
Bank 3
71M6521DE/71M6521FE
OV
-
(0x08 – 0x0F)
(0x18 – 0x1F)
(0x00 – 0x07)
(0x10 – 0x17)
Location
Energy Meter IC
P
LSB
DATASHEET
JANUARY 2008
v1.0