C501_1 Datasheet, PDF (13/121 Pages) Siemens Semiconductor Group – 8-Bit Single-Chip Microcontroller

Introduction
C501
Table 1-1
Pin Definitions and Functions (cont’d)
Symbol
Pin Number
I/O*) Function
P-LCC-44 P-DIP-40 P-MQFP-44
P3.0 – P3.7 11,
13–19
10–17 5, 7–13
11
10
5
13
11
7
14
12
8
15
13
9
16
14
10
17
15
11
18
16
12
19
17
13
I/O Port 3
is a quasi-bidirectional I/O port with
internal pull-up resistors. Port 3 pins that
have 1s written to them are pulled high by
the internal pull-up resistors, and in that
state they can be used as inputs. As
inputs, port 3 pins being externally pulled
low will source current (I_IL, in the DC
characteristics) because of the internal
pull-up resistors. Port 3 also contains the
interrupt, timer, serial port 0 and external
memory strobe pins which are used by
various options. The output latch
corresponding to a secondary function
must be programmed to a one (1) for that
function to operate.
The secondary functions are assigned to
the pins of port 3, as follows:
P3.0 R×D receiver data input (asyn-
chronous) or data input
output (synchronous) of
serial interface 0
P3.1 T×D transmitter data output
(asynchronous) or clock
output (synchronous) of
the serial interface 0
P3.2 INT0 interrupt 0 input/timer 0
gate control
P3.3 INT1 interrupt 1 input/timer 1
gate control
P3.4 T0 counter 0 input
P3.5 T1 counter 1 input
P3.6 WR the write control signal lat-
ches the data byte from
port 0 into the external
data memory
P3.7 RD the read control signal
enables the external data
memory to port 0
*) I = Input
O = Output
Semiconductor Group
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