DS80C320-QCG Datasheet, PDF (5/38 Pages) Maxim Integrated Products – High-Speed/Low-Power Microcontrollers

DS80C320/DS80C323 High-Speed/Low-Power Microcontrollers
PIN DESCRIPTION (continued)
PIN
DIP PLCC TQFP
NAME
FUNCTION
21
24
18 A8 (P2.0) _{Port 2, Output. Port 2 serves as the MSB for external addressing.}
22
25
19 A9 (P2.1) P2.7 is A15 and P2.0 is A8. The device will automatically place the
23
26
20 A10 (P2.2) MSB of an address on P2 for external ROM and RAM access.
24
27
21 A11 (P2.3) Although Port 2 can be accessed like an ordinary I/O port, the value
25
28
22 A12 (P2.4) stored on the Port 2 latch will never be seen on the pins (due to
26
29
23 A13 (P2.5) ^{memory access). Therefore, writing to Port 2 in software is only}
27
30
24 A14 (P2.6) ^{useful for the instructions MOVX A, @Ri or MOVX @Ri, A. These}
instructions use the Port 2 internal latch to supply the external address
28
31
25 A15 (P2.7) ^{MSB. In this case, the Port 2 latch value will be supplied as the}
address information.
Port 3, Input/Output. 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 & 1 Inputs, RD and WR strobes. The reset
condition of Port 3 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 both the output high and input state. The
alternate modes of Port 3 are outlined below:
10–17
11, 13–
19
5, 7–13
P3.0–P3.7
PIN
PORT ALTERNATE
DIP PLCC TQFP
MODE
10
11
5
P3.0
RXD0
Serial Port 0 Input
11
13
7
P3.1
TXD0
Serial Port 0 Output
12
14
8
P3.2
INT0
External Interrupt 0
13
15
9
P3.3
INT1
External Interrupt 1
14
16
10 P3.4
T0
Timer 0 External Input
31
35
29
—
12, 34, 6, 28,
1*
39*
EA
N.C.
15
17
11 P3.5
T1
Timer 1 External Input
16
18
12 P3.6
17
19
13 P3.7
External Data Memory Write
WR
Strobe
External Data Memory Read
RD
Strobe
External Access, Active-Low Input. This pin must be connected to
ground for proper operation.
No Connection (Reserved). These pins should not be connected.
They are reserved for use with future devices in this family.
*These pins are reserved for additional ground pins on future products.
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