6.1. Overview

The ARM720T write buffer is provided to improve system performance. It can buffer up to eight words of data, and four independent addresses. It may be enabled or disabled via the W bit (bit 3) in the ARM720T Control Register. The buffer is disabled and flushed on reset.

The operation of the write buffer is further controlled by the Bufferable (B) bit, which is stored in the Memory Management Page Tables. For this reason, the MMU must be enabled so you can use the write buffer. The two functions may however be enabled simultaneously, with a single write to the Control Register.

For a write to use the write buffer, both the W bit in the Control Register and the B bit in the corresponding page table must be set.

Note

It is not possible to abort buffered writes externally; the BERROR pin is ignored. Areas of memory which may generate aborts should be marked as unbufferable in the MMU page tables.

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