C517A Datasheet, PDF (11/67 Pages) Siemens Semiconductor Group – 8-Bit CMOS Microcontroller

C517A
Table 2
Pin Definitions and Functions (cont’d)
Symbol
P4.0 - P4.7
Pin Number
P-MQFP-100
64 - 66,
68 - 72
PE/SWD
67
RESET
73
V_AREF
V_AGND
P7.0 - P7.7
78
79
87 - 80
*) I = Input
O = Output
I/O*)
I/O
I
I
–
–
Function
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.
Power saving mode enable / Start watchdog timer
A low level at this pin allows the software to enter the power
saving modes (idle mode, slow down mode, and power
down mode). In case the low level is also seen during
reset, the watchdog timer function is off on default.
Usage of the software controlled power saving modes is
blocked, when this pin is held at 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. During hardware power down the
pullup resistor is switched off.
RESET
A low level on this pin for the duration of two machine
cycles while the oscillator is running resets the C517A. 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
Port 7
is an 8-bit unidirectional input port. Port pins can be used
for digital input, if voltage levels meet the specified input
high/low voltages, and for the lower 8-bit of the multiplexed
analog inputs of the A/D converter, simultaneously.
P7.0 - P7.7 AIN0 - AIN7 analog input 8 - 14
Semiconductor Group
11
1997-10-01