DS5000(T)

3 of 19

PIN DESCRIPTION

PIN

NAME

FUNCTION

1–8

P1.0–P1.7

General-Purpose I/O Port 1

9

RST

Active-High Reset Input. A logic 1 applied to this pin will activate a reset state.

This pin is pulled down internally so this pin can be left unconnected if not used.

10

P3.0/RXD

General-Purpose I/O Port Pin 3.0/Receive Signal for On-Board UART. This pin

should not be connected directly to a PC COM port.

11

P3.1/TXD

General-Purpose I/O Port Pin 3.1/Transmit Signal for On-Board UART. This pin

should not be connected directly to a PC COM port.

12

P3.2/

INT0

General-Purpose I/O Port Pin 3.2/Active-Low External Interrupt 0

13

P3.3/

INT1

General-Purpose I/O Port Pin 3.3/Active-Low External Interrupt 1

14

P3.4/T0

General-Purpose I/O Port Pin 3.4/Timer 0 Input

15

P3.5/T1

General-Purpose I/O Port Pin 3.5/Timer 1 Input

16

P3.6/

WR

General-Purpose I/O Port Pin 3.6/Active-Low Write Strobe for Expanded Bus

Operation

17

P3.7/

RD

General-Purpose I/O Port Pin 3.7/Active-Low Read Strobe for Expanded Bus

Operation

18, 19

XTAL2,

XTAL1

Crystal Connection. Used to connect an external crystal to the internal oscillator.

XTAL1 is the input to an inverting amplifier and XTAL2 is the output.

20

GND

Logic Ground

21–28

P2.0–P2.7/

A8–A15

General-Purpose I/O Port 2/MSB of the Expanded Address Bus

29

PSEN

Active-Low Program Store Enable. Used to enable an external program memory

when using the expanded bus. It is normally an output and should be unconnected

if not used.

PSEN also is used to invoke the bootstrap loader. At this time, PSEN is

pulled down externally. This should only be done once the DS5000(T) is already in

a reset state. The device that pulls down should be open drain since it must not

interfere with

PSEN under normal operation.

30

ALE

Address Latch Enable. Used to demultiplex the multiplexed expanded address/data

bus on Port 0. This pin is normally connected to the clock input on a ’373 type

transparent latch. When using a parallel programmer, this pin also assumes the

PROG function for programming pulses.

31

EA

Active-Low External Access. This pin forces the DS5000(T) to behave like an

8031. No internal memory (or clock) is available when this pin is at a logic low.

Since this pin is pulled down internally, it should be connected to +5V to use NV

pulses.

32-39

P0.7–P0.0/

AD7–AD0

General-Purpose I/O Port 0/Multiplexed Expanded Address/Data Bus. This port is

open drain and cannot drive a logic 1. It requires external pullups. When used in

the multiplexed expanded address data/bus mode, this pin does not require pullups.

40

+5V Power Supply