8XC51SLLOW VOLTAGE 8XC51SL

PIN DESCRIPTIONS

Table 1 Pin Descriptions

Symbol

Type

Description

Circuit ground potential

Supply voltage during normal Idle and Power-Down operation nominally a5V

g

PCDB0 – 7

IO

Host interface data bus An 8-bit bidirectional port for data transfers between the

host processor and the keyboard controller

WRL

I

The active-low host-interface write signal

RDL

I

The active-low host-interface read signal

CSL

I

The active-low host-interface chip select

A0 – A1

I

Host-Interface Address select inputs

PCOBF

O

The active-high host-interface Output Buffer Full interrupt

GATEA20

O

Gate A20 control signal output

RCLPROGL

O

Host resetactive low This pin is also the program pulse input during EPROM

programming

LED0 – 3

O

LED output drivers

KSI0 – 7

I

Keyboard input scan lines (input Port 0) Schmitt inputs with 5K – 20K pull-up

resistors

KSO0 – 15

O

Keyboard output scan lines

PORT 1

IO

Port 1 is a general-purpose 8-bit bidirectional port with internal pull-ups It also

supports the following user-selectable functions

P10A0 –

P10 – P16 are available for connection to dedicated keyboard inputs A0 – A7 output

the low-order address byte (refer to LOADREN signal)

P17A7

LOADREN

I

Low address enable When set high address bits A0 – A7 are output on P10 – P17

PORT2

IO

Port 2 is a general-purpose 8-bit bidirectional port with internal pull-ups on P20 – 6

A8 – 14 It also supports the following user-selectable functions

P20 – 6A8 – 14

P20 – 6A8 – 14 output the high-order address byte

P27LED4

P27LED4 is available as a fifth LED output driver (by writing to the port bit 7)

PORT 3

IO

Port 3 is a general-purpose 8-bit bidirectional port P32INT0 P34T0 P36WRL

and P37RDL have internal pull-ups P30SIF00 P31SIF01 P33SIF10 and

P35SIF11 are high-drive open-drain outputs It also supports the following user-

selectable functions

P30SIF00

A high-drive open-drain output to support an external serial keyboard interface

(typically CLK) RXD (8051 UART serial input port) SIF0INTL (serial interface

interrupt 0)

P31SIF01

A high-drive open-drain output to support an external serial keyboard interface

(typically DATA) TXD (8051 UART serial output port)

P32INT0

INT0L (external interrupt 0)

P33SIF10

A high-drive open-drain output to support an external serial keyboard interface

(typically mouse CLK) SIF1INTL (external interrupt 1)

P34T0

AUXOBF1 (output buffer fullmouse support) T0 (TimerCounter 0 external

input)

P35SIF11

A high-drive open-drain output to support an external serial keyboard interface

(typically mouse DATA) T1 (TimerCounter 1 external input)

P36WRL

WRL (external data memory write strobe) inactive at addresses 7FF0 – 7FFFH

P37RDL

AUXOBF2 (output buffer full interrupt) INT2L (external interrupt) RDL (external

data memory read strobe) inactive at addresses 7FF0 – FFFFH

4