TMPR4955AF datasheet(104/168 Pages) TOSHIBA

104 / 168 page

Chapter 6 TX4955A System Interface

6-32

6.2.14

Data Error Detection

The TX4955A internal system interface uses the following two methods to detect data

errors:

•

Indication of good data by data identifier SysCmd(5)

•

Determination by a check bit

6.2.14.1 Indication of good data by data identifier SysCmd(5)

This bit indicates whether data is good or not for all data. Therefore, in a block refill

transfer, for example, no matter in what number of data SysCmd(5) may have been set,

a bus error exception is always generated.

6.2.14.2 Determination by a check bit

When an error is detected by check bit determination, a bus error exception occurs.

Because this determination also is made for all data, no matter in what number of

data in a block refill transfer an error may have occurred, a bus error exception is

always generated.

6.2.14.3 Timing at which a bus error exception occurs

Indication of good data (SysCmd(5)): Two cycles after read data

Check bit error detection: Three cycles after read response data

6.2.14.4 Precautions

•

There is no means of identifying whether a bus error exception has been

generated by indication of good data or by check bit determination. Nor does

the TX49 core have a cache parity bit, but when a bus error exception occurs

during a block refill transfer, the cache line is referenced INVALID.

•

Regardless of whether a bus error exception has been generated by indication

of good data or by check bit determination during a block refill transfer, a

designated block size of data needs to be transferred.

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