DS80C320 Datasheet, PDF (4/38 Pages) Dallas Semiconductor – High-Speed/Low-Power Micro

DS80C320/DS80C323 High-Speed/Low-Power Microcontrollers
PIN DESCRIPTION (continued)
PIN
DIP PLCC TQFP
30 33
27
NAME
ALE
FUNCTION
Address Latch-Enable Output. This pin functions as a clock to latch
the external address LSB from the multiplexed address/data bus. This
signal is commonly connected to the latch enable of an external 373
family transparent latch. ALE has a pulse width of 1.5 XTAL1 cycles
and a period of four XTAL1 cycles. ALE is forced high when the
device is in a reset condition.
39 43
38 42
37 41
36 40
35 39
34 38
33 37
32 36
37
36
35
34
33
32
31
30
AD0
AD1
AD2
AD3
AD4
AD5
AD6
AD7
Port 0, Input/Output. Port 0 is the multiplexed address/data bus.
During the time when ALE is high, the LSB of a memory address is
presented. When ALE falls, the port transitions to a bidirectional data
bus. This bus is used to read external ROM and read/write external
RAM memory or peripherals. The Port 0 has no true port latch and
cannot be written directly by software. The reset condition of Port 0 is
high. No pullup resistors are needed.
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 mode, since any external circuit that
writes to the port will overcome the weak pullup. When software writes
a 0 to any port pin, the device will 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 will cause a strong transition driver to turn on,
followed by a weaker sustaining pullup. Once the momentary strong
driver turns off, the port once again becomes the output high (and
input) state. The alternate modes of Port 1 are outlined as follows:
1–8
2–9
40–44,
1–3
P1.0–P1.7
DIP
1
PIN
PLCC
2
TQFP
40
PORT
P1.0
ALTERNATE
T2
FUNCTION
External I/O for
Timer/Counter 2
2
3
41
P1.1
T2EX
Timer/Counter 2
Capture/Reload Trigger
3
4
42
P1.2
RXD1
Serial Port 1 Input
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
TXD1
INT2
INT3
INT4
INT5
Serial Port 1 Output
External Interrupt 2
(Positive-Edge Detect)
External Interrupt 3
(Negative-Edge Detect)
External Interrupt 4
(Positive-Edge Detect)
External Interrupt 5
(Negative-Edge Detect)
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