ADSP-BF535 Blackfin Processor Hardware Reference
18-79
External Bus Interface Unit
refreshed within the t
REF
period specified in the SDRAM timing specifi-
cations. This command is issued to all the external banks whether or not
they are enabled (
EBxE
in the SDRAM Memory Global Control register).
Before executing the Auto-Refresh command, the SDC executes a Pre-
charge All command to all external banks. 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
power-up sequence and after exiting Self-Refresh mode.
Self-Refresh Command
The Self-Refresh 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 cycles while the SDRAM is
in Self-Refresh mode. Before executing the Self-Refresh command, all
external banks are precharged. Self-Refresh mode is enabled by writing a 1
to the
SRFS
bit of the SDRAM Memory Global Control register
(
EBIU_SDGCTL
). The SDRAM remains in Self-Refresh mode for at least
t
RAS
and until an internal access to SDRAM space occurs. When an inter-
nal access occurs causing the SDC to exit the SDRAM from Self-Refresh
mode, the SDC waits to meet the t
XSR
specification (t
XSR
= t
RAS
+ t
RP
)
and then issues an Auto-Refresh command. After the Auto-Refresh com-
mand, the SDC waits for the t
RFC
specification (t
RFC
= t
RAS
+ t
RP
) to be
met before executing the Activate command for the transfer that caused
the SDRAM to exit Self-Refresh mode. Therefore the latency from when a
transfer is received by the SDC while in Self-Refresh mode until the Acti-
vate command occurs for that transfer is 2
(t
RC
+ t
RP
).
Note the
SCLK[0]
and
SCLK[1]
are not disabled by the SDC during
Self-Refresh mode. However, software may disable the clocks by clearing
the
SCTLE
and
SCK1E
bits in
EBIU_SDGCTL
. The application software should
ensure that all applicable clock timing specifications are met before the
transfer to SDRAM address space which causes the controller to exit
Содержание ADSP-BF535 Blackfin
Страница 80: ...Development Tools 1 26 ADSP BF535 Blackfin Processor Hardware Reference...
Страница 312: ...Working With Memory 6 86 ADSP BF535 Blackfin Processor Hardware Reference...
Страница 332: ...System Interfaces 7 20 ADSP BF535 Blackfin Processor Hardware Reference...
Страница 360: ...Dynamic Power Management Controller 8 28 ADSP BF535 Blackfin Processor Hardware Reference...
Страница 446: ...Beginning and Ending an SPI Transfer 10 40 ADSP BF535 Blackfin Processor Hardware Reference...
Страница 522: ...Timing Examples 11 76 ADSP BF535 Blackfin Processor Hardware Reference...
Страница 562: ...IrDA Support 12 40 ADSP BF535 Blackfin Processor Hardware Reference...
Страница 608: ...PCI I O Issues 13 46 ADSP BF535 Blackfin Processor Hardware Reference...
Страница 672: ...References 14 64 ADSP BF535 Blackfin Processor Hardware Reference...
Страница 810: ...SDRAM Controller SDC 18 86 ADSP BF535 Blackfin Processor Hardware Reference...
Страница 811: ...ADSP BF535 Blackfin Processor Hardware Reference 18 87 External Bus Interface Unit...
Страница 812: ...SDRAM Controller SDC 18 88 ADSP BF535 Blackfin Processor Hardware Reference...
Страница 860: ...DMA Bus Debug Registers 20 30 ADSP BF535 Blackfin Processor Hardware Reference...
Страница 908: ...SDRAM Controller External Bus Interface Unit B 36 ADSP BF535 Blackfin Processor Hardware Reference...