C505_9708 SIEMENS [Siemens Semiconductor Group], C505_9708 Datasheet - Page 63

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

6
This chapter gives detailed information about all on-chip peripherals of the C505 except for the
integrated interrupt controller, which is described separately in chapter 7.
6.1
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. This port has no available
bits at bit positions 2-7.
6.1.1
The C505 generally allows digital I/O on 34 lines grouped into 4 bidirectional 8-bit ports and one
2-bit port. Each port bit consists of a latch, an output driver and an input buffer. Read and write
accesses to the I/O ports P0-P4 are performed via their corresponding special function registers.
Depending on the specific ports, multiple functions are assigned to the port pins. Therefore, the
parallel I/O ports of the C505 can be grouped into three different types which are listed in table 6-1.
Table 6-1
C505 Port Structure Types
Type
A
B
C
Type A and B port pins are standard C501 compatible I/O port lines, which can be used for digital
I/O. The type A ports (port 0 and port 2) are also designed for accessing external data or program
memory. Type B port lines are located at port 3 and port 4 to provide alternate functions for the serial
interface and CAN controller I/O lines respectively, or are used as control outputs during external
data memory accesses.
The C505 provides eight analog input lines which are realized as mixed digital/analog inputs (type
C). 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 the specific port 1 pins are enabled by bits in the SFRs 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
On-Chip Peripheral Components
Parallel I/O
Port Structures
Description
Standard digital I/O ports which can also be used for external address/data bus.
Standard multifunctional digital I/O port lines
Mixed digital/analog I/O port lines with programmable analog input function
6-1
On-Chip Peripheral Components
C505 / C505C
1997-08-01