15-16
MCF5282 User’s Manual
MOTOROLA
SDRAM Controller Operation
request flag. This refresh cycle includes a delay from any precharge to the auto-refresh
command, the auto-refresh command, and then a delay until any
ACTV
command is
allowed. Any SDRAM access initiated during the auto-refresh cycle is delayed until the
cycle is completed.
Figure 15-8 shows the auto-refresh timing. In this case, there is an SDRAM access when
the refresh request becomes active. The request is delayed by the precharge to
ACTV
delay
programmed into the active SDRAM bank by the CAS bits. The
REF
command is then
generated and the delay required by DCR[RTIM] is inserted before the next
ACTV
command is generated. In this example, the next bus cycle is initiated, but does not generate
an SDRAM access until T
RC
is finished. Because both chip selects are active during the
REF
command, it is passed to both blocks of external SDRAM.
Figure 15-8. Auto-Refresh Operation
15.2.3.6 Self-Refresh Operation
Self-refresh is a method of allowing the SDRAM to enter into a low-power state, while at
the same time to perform an internal refresh operation and to maintain the integrity of the
data stored in the SDRAM. The DRAM controller supports self-refresh with DCR[IS].
When IS is set, the
SELF
command is sent to the SDRAM. When IS is cleared, the
SELFX
command is sent to the DRAM controller. Figure 15-9 shows the self-refresh operation.
A[31:0]
SRAS
SCAS
DRAMW
PALL
SDRAM_CS[0] or [1]
REF
ACTV
t
RCD
= 2
t
RC
= 6
CLKOUT
Summary of Contents for ColdFire MCF5281
Page 124: ...3 20 MCF5282 User s Manual MOTOROLA EMAC Instruction Set Summary ...
Page 141: ...MOTOROLA Chapter 5 Static RAM SRAM 5 5 SRAM Programming Model ...
Page 142: ...5 6 MCF5282 User s Manual MOTOROLA SRAM Programming Model ...
Page 168: ...6 26 MCF5282 User s Manual MOTOROLA Interrupts ...
Page 186: ...7 18 MCF5282 User s Manual MOTOROLA Functional Description ...
Page 228: ...9 22 MCF5282 User s Manual MOTOROLA Functional Description ...
Page 246: ...10 18 MCF5282 User s Manual MOTOROLA Low Power Wakeup Operation ...
Page 254: ...11 8 MCF5282 User s Manual MOTOROLA Memory Map and Registers ...
Page 264: ...12 10 MCF5282 User s Manual MOTOROLA Chip Select Registers ...
Page 280: ...13 16 MCF5282 User s Manual MOTOROLA Misaligned Operands ...
Page 314: ...14 34 MCF5282 User s Manual MOTOROLA MCF5282 External Signals ...
Page 339: ...MOTOROLA Chapter 15 Synchronous DRAM Controller Module 15 25 SDRAM Example ...
Page 340: ...15 26 MCF5282 User s Manual MOTOROLA SDRAM Example ...
Page 356: ...16 16 MCF5282 User s Manual MOTOROLA DMA Controller Module Functional Description ...
Page 408: ...17 52 MCF5282 User s Manual MOTOROLA Buffer Descriptors ...
Page 446: ...20 24 MCF5282 User s Manual MOTOROLA Interrupts ...
Page 474: ...22 18 MCF5282 User s Manual MOTOROLA Programming Model ...
Page 510: ...23 36 MCF5282 User s Manual MOTOROLA Operation ...
Page 526: ...24 16 MCF5282 User s Manual MOTOROLA I2C Programming Examples ...
Page 672: ...28 12 MCF5282 User s Manual MOTOROLA Functional Description ...
Page 718: ...29 46 MCF5282 User s Manual MOTOROLA Motorola Recommended BDM Pinout ...
Page 750: ...32 8 MCF5282 User s Manual MOTOROLA Ordering Information ...