DS2252T

121395 4/14

PIN ASSIGNMENT

1

P1.0

11

P1.5

21

P3.1 TXD

31

P3.6 WR

12

P0.4

22

ALE

32

P2.4

3

P1.1

13

P1.6

23

P3.2 INT0

33

P3.7 RD

4

P0.0

14

P0.5

24

PROG

34

P2.3

5

P1.2

15

P1.7

25

P3.3 INT1

35

XTAL2

6

P0.1

16

P0.6

26

P2.7

36

P2.2

7

P1.3

17

RST

27

P3.4 T0

37

XTAL1

8

P0.2

18

P0.7

28

P2.6

38

P2.1

9

P1.4

19

P3.0 RXD

29

P3.5 T1

39

GND

10

P0.3

20

SDI

30

P2.5

40

P2.0

PIN DESCRIPTION

PIN

DESCRIPTION

4, 6, 8, 10,

12, 14, 16, 18

P0.0 – P0.7. General purpose I/O Port 0. This port is open–drain and can not drive a logic 1.

It requires external pull–ups. Port 0 is also the multiplexed Expanded Address/Data bus.

When used in this mode, it does not require pull–ups.

1, 3, 5, 7, 9,

11, 13, 15

P1.0 – P1.7. General purpose I/O Port 1.

40, 38, 36,

34, 32, 30,

28, 26

P2.0 – P2.7. General purpose I/O Port 2. Also serves as the MSB of the Expanded Address

bus.

19

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.

21

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.

23

P3.2 INT0. General purpose I/O port pin 3.2. Also serves as the active low External Interrupt

0. This pin is also connected to the INTP output of the DS1283 Real Time Clock.

25

P3.3 INT1. General purpose I/O port pin 3.3. Also serves as the active low External

Interrupt 1.

27

P3.4 T0. General purpose I/O port pin 3.4. Also serves as the Timer 0 input.

29

P3.5 T1. General purpose I/O port pin 3.5. Also serves as the Timer 1 input.

31

P3.6 WR. General purpose I/O port pin. Also serves as the write strobe for Expanded bus

operation.

33

P3.7 RD. General purpose I/O port pin. Also serves as the read strobe for Expanded bus

operation.

17

RST – Active high reset input. A logic 1 applied to this pin will activate a reset state. This pin

is pulled down internally, can be left unconnected if not used. An RC power–on reset circuit

is not needed and is NOT recommended.

22

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.