89C52 datasheet(9/50 Pages) ISSI

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IS89C52

Integrated Silicon Solution, Inc. — 1-800-379-4774

MC013-1C

11/21/98

ISSI®

SPECIAL FUNCTION REGISTERS

(Continued)

Stack Pointer (SP)

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.

Data Pointer (DPTR)

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.

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

initiates the transmission.) When data is moved from

SBUF, it comes from the receive buffer.

Timer Registers

Counter registers for Timer/Counters 0 and 1, respectively.

Capture Registers

The register pair (RCAP2H, RCAP2L) are the Capture

registers for the Timer 2 Capture Mode. In this mode, in

response to a transition at the IS89C52's T2EX pin, TH2

and TL2 are copied into RCAP2H and RCAP2L. Timer 2

also has a 16-bit auto-reload mode, and RCAP2H and

RCAP2L hold the reload value for this mode.

Control Registers

Special Function Registers IP, IE, TMOD, TCON, 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.

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