Sdram Speed Attributes Register - Motorola MVME5100 Programmer's Reference Manual

System Memory Controller (SMC)
3

SDRAM Speed Attributes Register

Address
Bit
Name
Operation
Reset
3-68
Note that RAM A/B/C/D BASE are located at $FEF80018
(refer to the section titled SDRAM Base Address Register
(Blocks A/B/C/D) for more information). They operate the
same for blocks A-D as these bits do for blocks E-H.
Also note that the combination of RAM_X_BASE and
ram_x_siz should never be programmed such that SDRAM
responds at the same address as the CSR, ROM/Flash,
External Register Set, or any other slave on the PowerPC bus.
The SDRAM Speed Attributes Register should be programmed based on
the SDRAM device characteristics and the Hawk's operating frequency to
ensure reliable operation.
In order for writes to this register to work properly they should be
separated from any SDRAM accesses by a refresh before the write and by
another refresh after the write. The refreshes serve two purposes: 1) they
make sure that all of the SDRAMs are idle ensuring that mode-register-set
operations for cl3 updates work properly, and 2) they make sure that no
SDRAM accesses happen during the write. A simple way to meet these
requirments is to use the following sequence:
1. Make sure all accesses to SDRAM are done.
2. Wait for the "32-Bit Counter" (refer to section further on) to
increment at least 100 times.
3. Perform the write/writes to this register (and other SMC registers if
desired).
4. Wait again for the "32-Bit Counter" to increment at least 100 times
before resuming accesses to SDRAM.
$FEF800D0
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