C167CS datasheet(191/517 Pages) INFINEON

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C167CS

Derivatives

The External Bus Interface

User’s Manual

9-3

V2.0, 2000-07

9.2

External Bus Modes

When the external bus interface is enabled (bit BUSACTx = ‘1’) and configured (bitfield

BTYP), the C167CS uses a subset of its port lines together with some control lines to

build the external bus.

The bus configuration (BTYP) for the address windows (BUSCON4 … BUSCON1) is

selected via software typically during the initialization of the system.

The bus configuration (BTYP) for the default address range (BUSCON0) is selected via

PORT0 during reset, provided that pin EA is low during reset. Otherwise BUSCON0 may

be programmed via software just like the other BUSCON registers.

The 16 MByte address space of the C167CS is divided into 256 segments of 64 KByte

each. The 16-bit intra-segment address is output on PORT0 for multiplexed bus modes

or on PORT1 for demultiplexed bus modes. When segmentation is disabled, only one

64 KByte segment can be used and accessed. Otherwise additional address lines may

be output on Port 4 (addressing up to 16 MByte) and/or several chip select lines may be

used to select different memory banks or peripherals. These functions are selected

during reset via bitfields SALSEL and CSSEL of register RP0H, respectively.

Note: Bit SGTDIS of register SYSCON defines, if the CSP register is saved during

interrupt entry (segmentation active) or not (segmentation disabled).

Table 9-1

Summary of External Bus Modes

BTYP

Encoding

External Data Bus Width

External Address Bus Mode

0 0

8-bit Data

Demultiplexed Addresses

0 1

8-bit Data

Multiplexed Addresses

1 0

16-bit Data

Demultiplexed Addresses

1 1

16-bit Data

Multiplexed Addresses

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