ARM ARM926EJ-S User Manual

Tightly-Coupled Memory Interface
ARM DDI0198D Copyright © 2001-2003 ARM Limited. All rights reserved. 5-11
Figure 5-4 Relationship between DRDMAEN, DRDMACS, DRDMAADDR, DRADDR and DRCS
Internal to the ARM926EJ-S processor there are multiple sources for both the address
and chip-select outputs. The address and chip-select outputs of the TCM interface are
timing critical, however not all of the internal sources are timing critical. By combining
the DMA inputs with non-critical address and chip-select signals, DMA can be done
without impacting timing on these outputs. All other TCM interface outputs are non
timing critical, and can be multiplexed externally.
The logic used to combine the DMA chip-select with the internal chip-select signals is
designed so that if the DMA inputs are selected then the DMA chip-select is also
asserted. If this is not the case then the chip-select output value is non-deterministic
unless it is known that the TCM interface is an idle state, as indicated by the DRIDLE
or STANDBYWFI signals.
Figure 5-5 on page 5-12 shows an example of how DMA accesses interact with normal
DTCM accesses.
1
0
Late address
Early address
1
0
Early CS
Late CS
DRDMAADDR
DRADDR
DRDMAEN
DRDMACS
DRCS

ARM ARM926EJ-S Specifications

General

Brand	ARM
Model	ARM926EJ-S
Category	Computer Hardware
Language	English