C501G-1E SIEMENS [Siemens Semiconductor Group], C501G-1E Datasheet - Page 37

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

Port 1, 2 and 3 output drivers have internal pullup FET’s (see figure 6-5). Each I/O line can be used
independently as an input or output. To be used as an input, the port bit stored in the bit latch must
contain a one (1) (that means for figure 6-5: Q=0), which turns off the output driver FET n1. Then,
for ports 1, 2 and 3, the pin is pulled high by the internal pullups, but can be pulled low by an external
source. When externally pulled low the port pins source current (
ports are sometimes called “quasi-bidirectional”.
Figure 6-5
Basic Output Driver Circuit of Ports 1, 2, and 3
Semiconductor Group
Int. Bus
Latch
Latch
Read
Write
Read
to
Pin
D
CLK
Bit
Latch
6-3
Q
Q
On-Chip Peripheral Components
MCS01823
V
CC
n1
Internal
Pull Up
Arrangement
I
IL
or
I
Pin
TL
). For this reason these
C501