TMPR4955AF datasheet(73/168 Pages) TOSHIBA

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Chapter 6 TX4955A System Interface

6-1

Chapter 6. TX4955A System Interface

6.1

Terminology

The following terms are used in this section.

•

External agent: Logic device that is directly connected to the processor via the system

interface so a processor can issue (instructions).

•

System event: Event issued inside a processor which, when generated, means that

access to external system resources is required.

•

Sequence: Strict order of requests that the processor generates in order to provide

service for system events.

•

Protocol: Shift of signals for each cycle generated on the system interface so processor

requests or external requests can be asserted.

•

Syntax: Strict definition of the bit pattern on the encoded bus (command bus, etc.).

6.2

Explanation of System Interface of R5000 type protocol mode

In TX4955A, it is built in system interface function corresponding to TX4300 type protocol. A

selection of above-mentioned R5000 type protocol mode or TX4300 type protocol mode increases

by external pin (MODE43* : 117 pin).

MODE43* = 0: TX4300 type protocol

MODE43* = 1: R5000 type protocol

The TX4955A processor supports 32-bit address/data interfaces. This processor makes it

possible to construct a processor system by processors and main memory. System interfaces

consist of the following components:

•

32-bit address/data bus, SysAD

•

4-bit SysAD check bus, SysADC

•

9-bit command bus, SysCmd

•

1-bit SysCmd check parity, SysCmdP

•

6 handshake signals

– RdRdy*, WrRdy*

– ExtRqst*, Release*

– ValidIn*, ValidOut*

The TX4955A processor accesses external resources using the system interface in order to

correct cache misses, uncached operation, and other problems.

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