C509-L_97 Datasheet, PDF (19/290 Pages) Siemens Semiconductor Group – 8-Bit CMOS Microcontroller

Introduction
C509-L
Table 1-1
Pin Definitions and Functions (cont’d)
Symbol
P3.0 – P3.7
V_SS
V_CC
*) I = Input
O = Output
Pin Number
90-97
90
91
92
93
94
95
96
97
10, 28, 62, 88
11, 29, 63, 89
I/O*) Function
I/O Port 3
is an 8-bit bidirectional I/O port with internal pullup
resistors. Port 3 pins that have 1's written to them are
pulled high by the internal pullup resistors, and in that
state 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 pullup resistors.
Port 3 also contains two external interrupt inputs, the
timer 0/1 inputs, the serial port 0 receive/transmit line
and the external memory strobe pins. 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 port pins of
port 3 as follows
P3.0 R×D0 Receiver data input (asynchronous) or
data input/output (synchronous) of serial
interface 0
P3.1 T×D0 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 latches 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
PSENX PSENX (external program store enable)
enables the external code memory
when the external / internal XRAM
mode or external / internal programming
mode is selected.
– Circuit ground potential
– Supply terminal for all operating modes
Semiconductor Group
1-12
1997-10-01