DS5000FP

4 of 22

PIN DESCRIPTION

PIN

NAME

FUNCTION

15, 17, 19, 21,

25, 27, 29, 31

P1.0–P1.7 General-Purpose I/O Port 1

34

RST

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

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

36

P3.0/

RXD

General-Purpose I/O Port Pin 3.0. Also serves as the receive signal for the on

board UART. This pin should not be connected directly to a PC COM port.

38

P3.1/

TXD

General-Purpose I/O Port Pin 3.1. Also serves as the transmit signal for the on-

board UART. This pin should not be connected directly to a PC COM port.

39

P3.2/

INT0

General-Purpose I/O Port Pin 3.2. Also serves as the active-low External

Interrupt 0.

40

P3.3/

INT1

General-Purpose I/O Port Pin 3.3. Also serves as the active-low External

Interrupt 1.

41

P3.4/T0

General-Purpose I/O Port Pin 3.4. Also serves as the Timer 0 input.

44

P3.5/T1

General-Purpose I/O Port Pin 3.5. Also serves as the Timer 1 input.

45

General-Purpose I/O Port Pin. Also serves as the write strobe for expanded bus

operation.

46

General-Purpose I/O Port Pin. Also serves as the read strobe for expanded bus

operation.

47, 48

XTAL2,

XTAL1

Crystal Connections. Used to connect an external crystal to the internal

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

52, 53

GND

Logic Ground

49, 50, 51, 56,

58, 60, 64, 66

P2.0–P2.7

General-Purpose I/O Port 2. Also serves as the MSB of the expanded address

bus.

68

PSEN

Program Store Enable. This active-low signal is used to enable an external

program memory when using the expanded bus. It is normally an output and

done once the DS5000FP is already in a reset state. The device that pulls down

operation.

70

ALE

Address Latch Enable. Used to de-multiplex 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

73

EA

External Access. This pin forces the DS5000FP to behave like an 8031. No

internal memory (or clock) will be 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 RAM.