SAF-C502-2R20N Siemens Semiconductor Group, SAF-C502-2R20N Datasheet - Page 9

• Manufacturer Part Number: SAF-C502-2R20N
• Description: 8-Bit CMOS Microcontroller
• Manufacturer: Siemens Semiconductor Group

Pin Definitions and Functions (cont’d)
Symbol
P3.0 – P3.7
XTAL2
*)I = Input
O = Output
Semiconductor Group
P-LCC-44
11, 13–19
11
13
14
15
16
17
18
19
20
Pin Number
P-DIP-40
10–17
10
11
12
13
14
15
16
17
18
I/O*)
I/O
–
8
Function
Port 3
is a 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 can be used as
inputs. As inputs, port 3 pins being externally
pulled low will source current (
characteristics) because of the internal pull-up
resistors. Port 3 also contains the interrupt,
timer, serial port 0 and external memory strobe
pins that are used by various options. The out-
put latch corresponding to a secondary func-
tion 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
P3.1 T D
P3.2 INT0
P3.3 INT1
P3.4 T0
P3.5 T1
P3.6 WR
P3.7 RD
XTAL2
Output of the inverting oscillator amplifier
receiver data input
(asynchronous) or data input/
output (synchronous) of serial
interface 0
transmitter data output
(asynchronous) or clock output
(synchronous) of the serial
interface 0
interrupt 0 input/timer 0 gate
control
interrupt 1 input/timer 1 gate
control
counter 0 input
counter 1 input
the write control signal latches
the data byte from port 0 into the
external data memory
the read control signal enables
the external data memory to
port 0
I
IL
, in the DC
C502