SH61F83
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3.2.1. Accumulator (ACC)
ACC
is the accumulator register used for most of the arithmetic and logical instructions. Its initial value is 00h.
3.2.2. B Register (B)
The
B
register is an SFR which is used primarily in the multiply and divide instructions. It can also be used as a temporary
scratch pad register for the other instructions and its initial value is 00h.
3.2.3. Program Status Word (PSW)
The
PSW
is the register that holds information about the status of the Accumulator, the selected register banks and other
information. Its initial value is 00h.This register is described in details in the following figure.
PSW - Program Status Word Register
Bit 7
CY
Carry flag
Bit 6
AC
Auxiliary Carry flag (for BCD operations)
Bit 5
F0
Flag 0(Available to the user for general purposes)
Bit 4
RS1
Register Bank select control bit 1 & 0
Set/cleared by software to determine working bank.
(RS1, RS0):
(00) - Bank 0
Address
(00H - 07H)
(01) - Bank 1
Address
(08H - 0FH)
(10) - Bank 2
Address
(10H - 17H)
(11) - Bank 3
Address
(18H - 1FH)
Bit 3
RS0
Bit 2
OV
Overflow Flag
Bit 1
X
User definable flag
Bit 0
P
Parity Flag
Set/Cleared by hardware each instruction cycle to indicate an odd/even number of “one” bit I the
Accumulator, i.e., even parity.
3.2.4. Stack Pointer (SP)
The Stack Pointer is an 8-bit wide register that is used to point to the top of the stack where addresses are stored. After a
reset, the stack pointer is initialized to 07H, and so the stack begins at 08H. However the stack can reside at any location in
the Internal RAM and stack pointer can be programmed to suit the user’s needs.
3.2.5. Data Pointers (DPH, DPL)
One Data Pointers (DPTR) consist of
DPH
,
DPL
Its intended function is to hold a 16-bit address. It may be manipulated as a
16-bit register or as two independent 8-bit registers.
3.2.6. Port 0, Port1, Port2, Port3 and Port4 (P0, P1, P2, P3 and P4)
The five ports have five SFR’s associated with them. Data to be brought out onto the port pins is written to the latches.
