User manual

OFF
SPLIT
pwr down
INIT
ENABLED
OFF
Mode-1
TAG and
cache
memory is
corrupted
ENABLED
or
SPLIT
INIT
www.ti.com VIMS Software (SW) Remarks
Table 7-1. Valid Retention Combination for VIMS Memory
Retention Enabled
Mode Comment
TAG-RAM CACHE-RAM VIMS Logic
SW must
1 No No Yes compensate for loss
of data in RAMs.
Will work in GPRAM
2 No Yes Yes mode, without SW
intervention
3 Yes Yes Yes
7.2.2.1 Mode 1
Mode 1 is intended for use when the system is in off mode, cache mode.
When the cache is enabled (in cache mode), SW must manually change the VIMS mode to off mode
before entering retention. When the system is taken out of retention, SW must put VIMS back into either
cache mode, as this will invalidate the cache memories (see Figure 7-7).
Figure 7-7. SW Precautions With No RAM Retention
Mode 1 can also be used when the system is in GPRAM mode, but SW must take into account that the
data in the GPRAM is lost when the system is set in retention.
7.2.2.2 Mode 2
Mode 2 is intended for systems where cache is in GPRAM mode. VIMS is retained with retention power to
the GPRAM.
NOTE: If SW tries to put VIMS into enabled mode after retention, the system fails because TAG
memory is corrupted.
The correct procedure will be to put VIMS into off mode and then disabled mode (see Figure 7-8, GPRAM
Retention, for more details).
535
SWCU117A–February 2015–Revised March 2015 Versatile Instruction Memory System (VIMS)
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