SAB80C517-M16 SIEMENS [Siemens Semiconductor Group], SAB80C517-M16 Datasheet - Page 45

• Manufacturer Part Number: SAB80C517-M16
• Description: 8-Bit CMOS Single-Chip Microcontroller
• Manufacturer: SIEMENS [Siemens Semiconductor Group]

7.1.3
Several pins of ports 1, 3, 4, 5 and 6 are multifunctional. They are port pins and also serve to
implement special features as listed in table 7-1.
Figure 7-5 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 pull-down FET is on and the port pin is stuck at 0. (This
does not apply to ports 1.0 to 1.4 and ports 5.0 to 5.7 when operated in compare output mode; refer
to section 7.5.3 for details). After reset all port latches contain ones (1).
Figure 7-5
Circuitry of Ports 1, 3, 4, 5 and 6.0 through 6.2
Ports 6.3 through 6.7 have no alternate functions as discribed above. Therefore, the port circuitry
can do without the switching capability between alternate function and normal I/O operation. This
more simple circuitry is shown as basic port structure in figures 7-1 and 7-2.
Semiconductor Group
Alternate Functions
Int. Bus
Latch
Latch
Read
Read
Write
to
Pin
D
CLK
Bit
Latch
Alternate
Function
Input
Q
Q
46
Alternate
Function
Output
On-Chip Peripheral Components
&
MCS01827
V
CC
Internal
Pull Up
Arrangement
Pin