Preliminary W78LE58

Publication Release Date: June 2000

- 7 -

Revision A1

Continued

A8

+IE

00000000

P42AL

00000000

P42AH

00000000

P2ECON

0000xx00

AF

A0

+P2

11111111

A7

98

+SCON

00000000

SBUF

xxxxxxxx

9F

90

+P1

11111111

P41AL

00000000

P41AH

00000000

97

88

+TCON

00000000

TMOD

00000000

TL0

00000000

TL1

00000000

TH0

00000000

TH1

00000000

8F

80

+P0

11111111

SP

00000111

DPL

00000000

DPH

00000000

P40AL

00000000

P40AH

00000000

PCON

00110000

87

Notes:

1.The SFRs marked with a plus sign(+) are both byte- and bit-addressable.

2. The text of SFR with bold type characters are extension function registers.

Port 4

Port 4, address D8H, is a 4-bit multipurpose programmable I/O port. Each bit can be configured

individually by software. The Port 4 has four different operation modes.

Mode 0: P4.0

−P4.3 is a bi-directional I/O port which is same as port 1. P4.2 and P4.3 also serve as

Mode 1: P4.0

−P4.3 are read strobe signals that are synchronized with RD signal at specified

addresses. These signals can be used as chip-select signals for external peripherals.

Mode 2: P4.0

−P4.3 are write strobe signals that are synchronized with WR signal at specified

addresses. These signals can be used as chip-select signals for external peripherals.

Mode 3: P4.0

−P4.3 are read/write strobe signals that are synchronized with RD or WR signal at

specified addresses. These signals can be used as chip-select signals for external

peripherals.

When Port 4 is configured with the feature of chip-select signals, the chip-select signal address range

depends on the contents of the SFR P4xAH, P4xAL, P4CONA and P4CONB. The registers P4xAH

and P4xAL contain the 16-bit base address of P4.x. The registers P4CONA and P4CONB contain the

control bits to configure the Port 4 operation mode.

INT2 / INT3

Two additional external interrupts, INT2 and INT3 , whose functions are similar to those of external

interrupt 0 and 1 in the standard 80C52. The functions/status of these interrupts are

determined/shown by the bits in the XICON (External Interrupt Control) register. The XICON register

is bit-addressable but is not a standard register in the standard 80C52. Its address is at 0C0H. To

set/clear bits in the XICON register, one can use the "SETB ( CLR ) bit" instruction. For example,

"SETB 0C2H" sets the EX2 bit of XICON.