C505-2RM SIEMENS [Siemens Semiconductor Group], C505-2RM Datasheet - Page 29

• Manufacturer Part Number: C505-2RM
• Description: 8-Bit CMOS Microcontroller
• Manufacturer: SIEMENS [Siemens Semiconductor Group]

C505 / C505C
C505A / C505CA
I/O Ports
The C505 has four 8-bit I/O ports and one 2-bit I/O port. Port 0 is an open-drain bidirectional I/O
port, while ports 1 to 4 are quasi-bidirectional I/O ports with internal pullup resistors. That means,
when configured as inputs, ports 1 to 4 will be pulled high and will source current when externally
pulled low. Port 0 will float when configured as input.
The output drivers of port 0 and 2 and the input buffers of port 0 are also used for accessing external
memory. In this application, port 0 outputs the low byte of the external memory address, time
multiplexed with the byte being written or read. Port 2 outputs the high byte of the external memory
address when the address is 16 bits wide. Otherwise, the port 2 pins continue emitting the P2 SFR
contents. In this function, port 0 is not an open-drain port, but uses a strong internal pullup FET.
Port 4 is 2-bit I/O port with CAN controller specific alternate functions. The eight analog input lines
are realized as mixed digital/analog inputs. The 8 analog inputs, AN0-AN7, are located at the port 1
pins P1.0 to P1.7. After reset, all analog inputs are disabled and the related pins of port 1 are
configured as digital inputs. The analog function of a specific port 1 pin is enabled by bits in the SFR
P1ANA. Writing a 0 to a bit position of P1ANA assigns the corresponding pin to operate as analog
input.
Note: P1ANA is a mapped SFR and can be only accessed if bit RMAP in SFR SYSCON is set.
Semiconductor Group
29
1997-12-01