IC80C51
IC80C31
SPECIAL FUNCTION REGISTERS
(Continued)
Stack Pointer (SP)
initiates the transmission.) When data is moved from
SBUF, it comes from the receive buffer.
The Stack Pointer Register is eight bits wide. It is
incremented before data is stored during PUSH and CALL
executions. While the stack may reside anywhere in on-
chip RAM, the Stack Pointer is initialized to 07H after a
reset. This causes the stack to begin at location 08H.
Timer Registers
Register pairs (TH0, TL0) and (TH1, TL1),are the 16-bit
CounterregistersforTimer/Counters0,1and2, respectively.
Data Pointer (DPTR)
Control Registers
The Data Pointer consists of a high byte (DPH) and a low
byte (DPL). Its function is to hold a 16-bit address. It may
be manipulated as a 16-bit register or as two independent
8-bit registers.
Special Function Registers IP, IE, TMOD, TCON, T2CON,
SCON, and PCON contain control and status bits for the
interrupt system, the Timer/Counters, and the serial port.
They are described in later sections of this chapter.
Ports 0 To 3
P0, P1, P2, and P3 are the SFR latches of Ports 0, 1, 2, and
3, respectively.
Serial Data Buffer (SBUF)
The Serial Data Buffer is actually two separate registers, a
transmit buffer and a receive buffer register. When data is
moved to SBUF, it goes to the transmit buffer, where it is
held for serial transmission. (Moving a byte to SBUF
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