DS2251 View Datasheet(PDF) - Dallas Semiconductor -> Maxim Integrated
Part Name
Description
Manufacturer
DS2251 Datasheet PDF : 20 Pages
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PIN ASSIGNMENT
1 P1.0
19
2 P1.1
20
3 P1.2
21
4 P1.3
22
5 P1.4
23
6 P1.5
24
7 P1.6
25
8 P1.7
26
9 RST
27
10 P3.0 RXD
28
11 P3.1 TXD
29
12 P3.2 INT0
30
13 P3.3 INT1
31
14 P3.4 T0
32
15 P3.5 T1
33
16 P3.6 WR
34
17 P3.7 RD
35
18 XTAL1
36
XTAL2
GND
P2.0
P2.1
P2.2
P2.3
P2.4
P2.5
P2.6
P2.7
PSEN
ALE
PROG
P0.7
P0.6
P0.5
P0.4
P0.3
37 P0.2
38 P0.1
39 P0.0
40 VCC
41 BA0
42 BA1
43 BA2
44 BA3
45 BA4
46 BA5
47 BA6
48 BA7
49 BA8
50 BA9
51 BA10
52 BA11
53 BA12
54 BA13
55 INTB
56 BD0
57 BD1
58 BD2
59 BD3
60 BD4
61 BD5
62 BD6
63 BD7
64 R/ W
65 PF
66 PE3
67 PE4
68 INTP
69 INTA
70 SQW
71 VRST
72 BA15
DS2251T
PIN DESCRIPTION
PIN
DESCRIPTION
39-32
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.
1-8 P1.0 - P1.7. General purpose I/O Port 1.
21-28 P2.0 - P2.7. General purpose I/O Port 2. Also serves as the MSB of the Expanded Address
bus.
10 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.
11 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.
12 P3.2 INT0 . General purpose I/O port pin 3.2. Also serves as the active low External
Interrupt 0.
13 P3.3 INT1 . General purpose I/O port pin 3.3. Also serves as the active low External
Interrupt 1.
14 P3.4 T0. General purpose I/O port pin 3.4. Also serves as the Timer 0 input.
15 P3.5 T1. General purpose I/O port pin 3.5. Also serves as the Timer 1 input.
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