C167CS datasheet(141/517 Pages) INFINEON

141 / 517 page

C167CS

Derivatives

Parallel Ports

User’s Manual

7-14

V2.0, 2000-07

and segment addresses. Software can read this register in order to react according to

the selected configuration, if required.

When the reset is terminated, the internal pullup devices are switched off, and PORT0

will be switched to the appropriate operating mode.

During external accesses in multiplexed bus modes PORT0 first outputs the 16-bit

intra-segment address as an alternate output function. PORT0 is then switched to

high-impedance input mode to read the incoming instruction or data. In 8-bit data bus

mode, two memory cycles are required for word accesses, the first for the low byte and

the second for the high byte of the word. During write cycles PORT0 outputs the data

byte or word after outputting the address.

During external accesses in demultiplexed bus modes PORT0 reads the incoming

instruction or data word or outputs the data byte or word.

Figure 7-6

PORT0 IO and Alternate Functions

While external bus cycles are executed, PORT0 is controlled by the bus controller. The

port direction is determined by the type of the bus cycle, the data are transferred directly

from/to the bus controller hardware. The alternate output data can be the 16-bit

intrasegment address or the 8/16-bit data information. While PORT0 is not used by the

bus controller, it is controlled by its direction and output latch registers. User software

must therefore be very careful when writing to PORT0 registers while the external bus is

enabled. In most cases keeping the reset values will be the best choice.

Figure 7-7 shows the structure of a PORT0 pin.

MCA04344

P0H.7

P0H.6

P0H.5

P0H.4

P0H.3

P0H.2

P0H.1

P0H.0

P0L.7

P0L.6

P0L.5

P0L.4

P0L.3

P0L.2

P0L.1

P0L.0

Port 0

P0H

P0L

Alternate Function

General Purpose

Input/Output

8-Bit

Demux Bus

16-Bit

Demux Bus

D10

D11

D12

D13

D14

D15

A15

A14

A13

A12

A11

A10

AD7

AD6

AD5

AD4

AD3

AD2

AD1

AD0

8-Bit

MUX Bus

AD15

AD14

AD13

AD12

AD11

AD10

AD9

AD8

AD7

AD6

AD5

AD4

AD3

AD2

AD1

AD0

16-Bit

MUX Bus

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