Rainbow Electronics DS89C450 - Manual (Page 13)

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)
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)
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.
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
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
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.