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
Summary of Contents for ADSP-BF535 Blackfin
Page 80: ...Development Tools 1 26 ADSP BF535 Blackfin Processor Hardware Reference...
Page 312: ...Working With Memory 6 86 ADSP BF535 Blackfin Processor Hardware Reference...
Page 332: ...System Interfaces 7 20 ADSP BF535 Blackfin Processor Hardware Reference...
Page 360: ...Dynamic Power Management Controller 8 28 ADSP BF535 Blackfin Processor Hardware Reference...
Page 446: ...Beginning and Ending an SPI Transfer 10 40 ADSP BF535 Blackfin Processor Hardware Reference...
Page 522: ...Timing Examples 11 76 ADSP BF535 Blackfin Processor Hardware Reference...
Page 562: ...IrDA Support 12 40 ADSP BF535 Blackfin Processor Hardware Reference...
Page 608: ...PCI I O Issues 13 46 ADSP BF535 Blackfin Processor Hardware Reference...
Page 672: ...References 14 64 ADSP BF535 Blackfin Processor Hardware Reference...
Page 810: ...SDRAM Controller SDC 18 86 ADSP BF535 Blackfin Processor Hardware Reference...
Page 811: ...ADSP BF535 Blackfin Processor Hardware Reference 18 87 External Bus Interface Unit...
Page 812: ...SDRAM Controller SDC 18 88 ADSP BF535 Blackfin Processor Hardware Reference...
Page 860: ...DMA Bus Debug Registers 20 30 ADSP BF535 Blackfin Processor Hardware Reference...