Dallas DS5000(T) Manual page 3

PIN DESCRIPTION
PIN NAME
1–8 P1.0–P1.7
9 RST
10 P3.0/RXD
11 P3.1/TXD
12 P3.2/INT0
13 P3.3/INT1
14 P3.4/T0
15 P3.5/T1
16 P3.6/WR
17 P3.7/RD
XTAL2,
18, 19
XTAL1
20 GND
P2.0–P2.7/
21–28
A8–A15
29 PSEN
30 ALE
EA
31
P0.7–P0.0/
32-39
AD7–AD0
40 V
CC
General-Purpose I/O Port 1
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.
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.
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.
General-Purpose I/O Port Pin 3.2/Active-Low External Interrupt 0
General-Purpose I/O Port Pin 3.3/Active-Low External Interrupt 1
General-Purpose I/O Port Pin 3.4/Timer 0 Input
General-Purpose I/O Port Pin 3.5/Timer 1 Input
General-Purpose I/O Port Pin 3.6/Active-Low Write Strobe for Expanded Bus
Operation
General-Purpose I/O Port Pin 3.7/Active-Low Read Strobe for Expanded Bus
Operation
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.
Logic Ground
General-Purpose I/O Port 2/MSB of the Expanded Address Bus
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.
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.
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
RAM. In a parallel programmer, this pin also serves as V
pulses.
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.
+5V Power Supply
FUNCTION
3 of 19
DS5000(T)
for super voltage
PP