C508 datasheet(30/93 Pages) INFINEON

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C508

Data Sheet

2000-08

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 provides the analog input channels to the A/D converter.

Port Structures

The C508 generally allows digital I/O on 32 lines grouped into 4 bi-directional 8-bit ports

and analog/digital input on one uni-directional 8-bit port. Except for Port 4 which is the

uni-directional input 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-P5 (except P4) are performed via

their corresponding special function registers.

When Port 4 is used as analog input, an analog channel is switched to the A/D converter

through a 3-bit multiplexer, which is controlled by three bits in SFR ADCON. Port 4 lines

may also be used as digital inputs. In this case they are addressed as an input port via

SFR P4. Since Port 4 has no internal latch, the contents of SFR P4 only depends on the

levels applied to the input lines. It makes no sense to output a value to these input-only

port by writing to the SFR P4. This will have no effect.

The parallel I/O ports of the C508 can be grouped into four different types which are

listed in Table 4.

Type A and B port pins are standard C501 compatible I/O port lines, which can be used

for digital I/O. Type A port (Port 0) is also designed for accessing external data or

program memory. Type B port lines are located at Port 2, Port 3 and Port 5 to provide

alternate functions for the serial interface, LED drive interface, PWM signals, or are used

as control outputs during external data memory accesses. Type C port (Port 4) provides

the analog input port. Type D port lines can be switched to push-pull drive capability

when they are used as compare outputs of the CAPCOM unit.

Table 4

C508 Port Structure Types

Type

Description

Standard digital I/O ports which can also be used for external address/data bus.

Standard multifunctional digital I/O port lines.

Digital/analog uni-directional input port.

Standard digital I/O with push-pull drive capability.

C508 Datasheet(PDF) 30 Page - Infineon Technologies AG