C515A_9708 Datasheet, PDF (10/182 Pages) Siemens Semiconductor Group – 8-Bit CMOS Microcontroller

Introduction
C515A
1.2 Pin Definitions and Functions
This section describes all external signals of the C515A with its function.
Table 1-1
Pin Definitions and Functions
Symbol
P4.0-P4.7
PE/SWD
RESET
VAREF
VAGND
*) I = Input
O = Output
Pin Number
(P-MQFP-80)
72-74,
76-80
72
75
1
3
4
I/O*) Function
I/O Port 4
is an 8-bit quasi-bidirectional I/O port with internal pull-
up resistors. Port 4 pins that have 1’s written to them are
pulled high by the internal pull-up resistors, and in that
state can be used as inputs. As inputs, port 4 pins being
externally pulled low will source current (I _IL, in the DC
characteristics) because of the internal pull-up resistors.
P4 also contains the external A/D converter control pin.
The output latch corresponding to a secondary function
must be programmed to a one (1) for that function to
operate. The secondary function is assigned to port 4 as
follows :
P4.0 / ADST external A/D converter start pin
I
Power Saving Mode Enable / Start Watchdog Timer
A low level on this pin allows the software to enter the
power down, idle, and slow down mode. In case the low
level is also seen during reset, the watchdog timer
function is off on default.
Use of the software controlled power saving modes is
blocked when this pin is held on high level. A high level
during reset performs an automatic start of the watchdog
timer immediately after reset.
When left unconnected this pin is pulled high by a weak
internal pull-up resistor.
Note : If PE/SWD is low and V_AREF is low the oscillator
watchdog is disabled (testmode) !
I
RESET
A low level on this pin for the duration of two machine
cycles while the oscillator is running resets the C515A.
A small internal pullup resistor permits power-on reset
using only a capacitor connected to V_SS .
– Reference Voltage for the A/D converter
– Reference Ground for the A/D converter
Semiconductor Group
1-5
1997-08-01