ds2251 Maxim Integrated Products, Inc., ds2251 Datasheet - Page 4

• Manufacturer Part Number: ds2251
• Description: 128k Soft Microcontroller Module
• Manufacturer: Maxim Integrated Products, Inc.

PIN ASSIGNMENT
PIN DESCRIPTION
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
39-32
21-28
PIN
1-8
10
11
12
13
14
15
P1.0
P1.1
P1.2
P1.3
P1.4
P1.5
P1.6
P1.7
RST
P3.0 RXD
P3.1 TXD
P3.2
P3.3
P3.4 T0
P3.5 T1
P3.6
P3.7
XTAL1
P0.0 - P0.7. General purpose I/O Port 0. This port is open-drain and cannot drive a logic 1.
It requires external pullups. Port 0 is also the multiplexed Expanded Address/Data bus.
When used in this mode, it does not require pullups.
P1.0 - P1.7. General purpose I/O Port 1.
P2.0 - P2.7. General purpose I/O Port 2. Also serves as the MSB of the Expanded Address
bus.
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.
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.
P3.2
Interrupt 0.
P3.3
Interrupt 1.
P3.4 T0. General purpose I/O port pin 3.4. Also serves as the Timer 0 input.
P3.5 T1. General purpose I/O port pin 3.5. Also serves as the Timer 1 input.
INT0
INT1
WR
RD
INT0
INT1
. General purpose I/O port pin 3.3. Also serves as the active low External
. General purpose I/O port pin 3.2. Also serves as the active low External
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
XTAL2
GND
P2.0
P2.1
P2.2
P2.3
P2.4
P2.5
P2.6
P2.7
ALE
P0.7
P0.6
P0.5
P0.4
P0.3
PSEN
PROG
DESCRIPTION
4 of 20
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
P0.2
P0.1
P0.0
V
BA0
BA1
BA2
BA3
BA4
BA5
BA6
BA7
BA8
BA9
BA10
BA11
BA12
BA13
CC
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
BD0
BD1
BD2
BD3
BD4
BD5
BD6
BD7
R/
SQW
BA15
INTB
PF
PE3
PE4
INTP
INTA
VRST
W
DS2251T