C505_9708 SIEMENS [Siemens Semiconductor Group], C505_9708 Datasheet - Page 68

• Manufacturer Part Number: C505_9708
• Description: 8-Bit CMOS Microcontroller
• Manufacturer: SIEMENS [Siemens Semiconductor Group]

6.1.2.2
The pins of ports 1, 3 and 4 are multifunctional. They are port pins and also serve to implement
special features as listed in table 6-2.
Figure 6-4 shows a functional diagram of a port latch with alternate function. To pass the alternate
function to the output pin and vice versa, however, the gate between the latch and driver circuit must
be open. Thus, to use the alternate input or output functions, the corresponding bit latch in the port
SFR has to contain a one (1); otherwise the pulldown FET is on and the port pin is stuck at 0. After
reset all port latches contain ones (1).
Figure 6-4
Ports 1, 3 and 4
The alternate functions of Port 4 pins are available for the C505C only.
Semiconductor Group
Port 1, Port 3 and Port 4 Circuitry
Int. Bus
Latch
Latch
Read
Write
Read
to
Pin
D
CLK
Bit
Latch
Alternate
Function
Input
Q
Q
6-6
Alternate
Function
Output
On-Chip Peripheral Components
&
MCS01827
V
CC
Internal
Pull Up
Arrangement
Pin
C505 / C505C
1997-08-01