C501G-1E SIEMENS [Siemens Semiconductor Group], C501G-1E Datasheet - Page 38

• Manufacturer Part Number: C501G-1E
• Description: 8-Bit Single-Chip Microcontroller
• Manufacturer: SIEMENS [Siemens Semiconductor Group]

In fact, the pullups mentioned before and included in figure 6-5 are pullup arrangements as shown
in figure 6-6. One n-channel pulldown FET and three pullup FETs are used:
Figure 6-6
Output Driver Circuit of Ports 1 to 5 and 7
Semiconductor Group
– The pulldown FET n1 is of n-channel type. It is a very strong driver transistor which is capable
– The pullup FET p1 is of p-channel type. It is activated for two oscillator periods (S1P1 and
– The pullup FET p2 is of p-channel type. It is always activated when a “1” is in the port latch,
– The pullup FET p3 is of p-channel type. It is only activated if the voltage at the port pin is
Q
Input Data
(Read Pin)
of sinking high currents (
circuit to
the FET. This also means that no ”0“ must be programmed into the latch of a pin that is used
as input.
S1P2) if a 0-to-1 transition is programmed to the port pin, i.e. a “1” is programmed to the port
latch which contained a “0”. The extra pullup can drive a similar current as the pulldown FET
n1. This provides a fast transition of the logic levels at the pin.
thus providing the logic high output level. This pullup FET sources a much lower current than
p1; therefore the pin may also be tied to ground, e.g. when used as input with logic low input
level.
higher than approximately 1.0 to 1.5 V. This provides an additional pullup current if a logic
high level shall be output at the pin (and the voltage is not forced lower than approximately
1.0 to 1.5 V). However, this transistor is turned off if the pin is driven to a logic low level, e.g
when used as input. In this configuration only the weak pullup FET p2 is active, which sources
the current
(
with a low level applied. However, the driving capability is stronger if a logic high level is
output.
I
TL
). Thus, an additional power consumption can be avoided if port pins are used as inputs
V
CC
=1
I
IL
must be avoided if the transistor is turned on, since the high current might destroy
. If, in addition, the pullup FET p3 is activated, a higher current can be sourced
Delay = 1 State
I
OL
); it is only activated if a “0” is programmed to the port pin. A short
<
=1
_
1
6-4
V
On-Chip Peripheral Components
SS
p1
n1
p2
=1
V
CC
p3
MCS03230
Port
Pin
C501