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ADSP-BF537 Blackfin Processor Hardware Reference
6-53
External Bus Interface Unit
SDC refresh counter times out. The
RDIV
value in the SDRAM refresh
rate control register must be set so that all addresses are refreshed within
the t
REF
period specified in the SDRAM timing specifications. This com-
mand is issued to the external bank whether or not it is enabled (
EBE
in the
SDRAM memory global control register). Before executing the
auto-refresh command, the SDC executes a precharge all command to the
external bank. The next activate command is not given until the t
RFC
specification (t
RFC
= t
RAS
+ t
RP
) is met.
Auto-refresh commands are also issued by the SDC as part of the powerup
sequence and also after exiting self-refresh mode.
Self-Refresh Mode
The self-refresh mode is controlled by the self-refresh entry and
self-refresh exit commands. The SDC must issue a series of commands
including the self-refresh entry command to put the SDRAM into this low
power operation, and it must issue another series of commands including
the self-refresh exit command to re-access the SDRAM.
Self-Refresh Entry Command
The self-refresh entry command causes refresh operations to be performed
internally by the SDRAM, without any external control. This means that
the SDC does not generate any auto-refresh commands while the SDRAM
is in self-refresh mode. Before executing the self-refresh entry command,
all internal banks are precharged. The self-refresh entry command is
started by writing a 1 to the
SRFS
bit of the SDRAM memory global con-
trol register (
EBIU_SDGCTL
). The SDC now drives
SCKE
low.
L
Only the
SCKE
pin keeps control during self-refresh, all other
SDRAM pins are allowed to be disabled. However the SDC still
drives the
SCLK
during self-refresh mode. However, software may
disable the clock by clearing the
SCTLE
bit in
EBIU_SDGCTL
.
Содержание Blackfin ADSP-BF537
Страница 42: ...Contents xlii ADSP BF537 Blackfin Processor Hardware Reference ...
Страница 90: ...Development Tools 1 32 ADSP BF537 Blackfin Processor Hardware Reference ...
Страница 138: ...Programming Examples 4 26 ADSP BF537 Blackfin Processor Hardware Reference ...
Страница 340: ...SDC Programming Examples 6 84 ADSP BF537 Blackfin Processor Hardware Reference ...
Страница 606: ...Programming Examples 9 94 ADSP BF537 Blackfin Processor Hardware Reference ...
Страница 660: ...Programming Examples 10 54 ADSP BF537 Blackfin Processor Hardware Reference ...
Страница 720: ...Electrical Specifications 11 60 ADSP BF537 Blackfin Processor Hardware Reference ...
Страница 840: ...Programming Examples 13 42 ADSP BF537 Blackfin Processor Hardware Reference ...
Страница 876: ...Programming Examples 14 36 ADSP BF537 Blackfin Processor Hardware Reference ...
Страница 938: ...Programming Examples 15 62 ADSP BF537 Blackfin Processor Hardware Reference ...
Страница 958: ...Programming Examples 17 12 ADSP BF537 Blackfin Processor Hardware Reference ...
Страница 986: ...Programming Examples 18 28 ADSP BF537 Blackfin Processor Hardware Reference ...
Страница 1162: ...G 26 ADSP BF537 Blackfin Processor Hardware Reference ...
Страница 1218: ...Index I 56 ADSP BF537 Blackfin Processor Hardware Reference ...