DS5000FP

4 of 22

PIN DESCRIPTION

PIN

DESCRIPTION

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 will activate 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

Interrupt 0.

40

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

operation.

46

operation.

47, 48

XTAL2, XTAL1. 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 should be

PSEN

will be pulled down externally. This should only be done once the DS5000FP is

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

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 assumes the

PROG

function for programming pulses.

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. In a parallel