
DS89C430/DS89C440/DS89C450 Ultra-High-Speed Flash Microcontrollers 
13 of 48 
PIN DESCRIPTION (continued) 
PIN 
PDIP 
PLCC 
TQFP 
NAME 
FUNCTION 
1 
2 
40 
P1.0 
2 
3 
41 
P1.1 
3 
4 
42 
P1.2 
4 
5 
43 
P1.3 
5 
6 
44 
P1.4 
6 
7 
1 
P1.5 
7 
8 
2 
P1.6 
8 
9 
3 
P1.7 
Port 1, I/O.
 Port 1 functions as both an 8-bit, bidirectional I/O port and an alternate 
functional interface for timer 2 I/O, new external interrupts, and new serial port 1. The 
reset condition of port 1 is with all bits at logic 1. In this state, a weak pullup holds the port 
high. This condition also serves as an input state, since any external circuit that writes to 
the port overcomes the weak pullup. When software writes a 0 to any port pin, the 
DS89C430/DS89C440/DS89C450 activate a strong pulldown that remains on until either 
a 1 is written or a reset occurs. Writing a 1 after the port has been at 0 causes a strong 
transition driver to turn on, followed by a weaker sustaining pullup. Once the momentary 
strong driver turns off, the port again becomes the output high (and input) state. The 
alternate functions of port 1 are as follows: 
PORT 
ALTERNATE 
FUNCTION 
P1.0 
T2 
External I/O for Timer/Counter2 
P1.1 
T2EX 
Timer 2 Capture/Reload Trigger 
P1.2 
RXD1 
Serial Port 1 Receive  
P1.3 
TXD1 
Serial Port 1 Transmit  
P1.4 
INT2 
External Interrupt 2 (Positive Edge Detect) 
P1.5 
INT3 
External Interrupt 3 (Negative Edge Detect) 
P1.6 
INT4 
External Interrupt 4 (Positive Edge Detect) 
 P1.7 
INT5 
External Interrupt 5 (Negative Edge Detect) 
Port 2 (A8–A15), I/O.
 Port 2 is an 8-bit, bidirectional I/O port. The reset condition of port 2 
is logic high. In this state, a weak pullup holds the port high. This condition also serves as 
an input mode, since any external circuit that writes to the port overcomes the weak 
pullup. When software writes a 0 to any port pin, the DS89C430/DS89C440/DS89C450 
activate a strong pulldown that remains on until either a 1 is written or a reset occurs. 
Writing a 1 after the port has been at 0 causes a strong transition driver to turn on, 
followed by a weaker sustaining pullup. Once the momentary strong driver turns off, the 
port again becomes both the output high and input state. As an alternate function, port 2 
can function as the MSB of the external address bus when reading external program 
memory and read/write external RAM or peripherals. In page mode 1, port 2 provides both 
the MSB and LSB of the external address bus. In page mode 2, it provides the MSB and 
data. 
Port 3, I/O.
 Port 3 functions as both an 8-bit, bidirectional I/O port and an alternate 
functional interface for external interrupts, serial port 0, timer 0 and 1 inputs, and 
RD
 and 
WR
 strobes. The reset condition of port 3 is with all bits at a logic 1. In this state, a weak 
pullup holds the port high. This condition also serves as an input mode, since any external 
circuit that writes to the port overcomes the weak pullup. When software writes a 0 to any 
port pin, the DS89C430/DS89C440/DS89C450 activate a strong pulldown that remains on 
until either a 1 is written or a reset occurs. Writing a 1 after the port has been at 0 causes 
a strong transition driver to turn on, followed by a weaker sustaining pullup. Once the 
momentary strong driver turns off, the port again becomes both the output high and input 
state. The alternate modes of port 3 are as follows: 
PORT
ALTERNATE
FUNCTION
P3.0 
RXD0 
Serial Port 0 Receive  
P3.1 
TXD0 
Serial Port 0 Transmit  
P3.2 
INT0
External Interrupt 0 
P3.3 
INT1 
External Interrupt 1 
P3.4 
T0
Timer 0 External Input 
P3.5 
T1 
Timer 1 External Input 
P3.6 
WR
External Data Memory Write Strobe 
P3.7 
RD 
External Data Memory Read Strobe 
21 
24 
18 
P2.0 (A8) 
22 
25 
19 
P2.1 (A9) 
23 
26 
20 
P2.2(A10) 
24 
27 
21 
P2.3(A11) 
25 
28 
22 
P2.4(A12) 
26 
29 
23 
P2.5(A13) 
27 
30 
24 
P2.6(A14) 
28 
31 
25 
P2.7(A15) 
10 
11 
5 
P3.0 
11 
13 
7 
P3.1 
12 
14 
8 
P3.2 
13 
15 
9 
P3.3 
14 
16 
10 
P3.4 
15 
17 
11 
P3.5 
16 
18 
12 
P3.6 
17 
19 
13 
P3.7 
31 
35 
29 
EA 
External Access.
 Allows selection of internal or external program memory. Connect to 
ground to force the DS89C430/DS89C440/DS89C450 to use an external memory program 
memory. The internal RAM is still accessible as determined by register settings. Connect 
to V
CC
 to use internal flash memory.