3-20
Falcon ECC Memory Controller Chip Set
3
Refresh/Scrub
Refresh/Scrub is done differently based on which DRAM blocks are
populated: (A and/or B) but not (C and D), or (A and/or B) and (C and/or
D).
Blocks A and/or B Present, Blocks C and D Not Present
The Falcon pair performs refresh by doing a burst of four RAS_ cycles
approximately once every 60
µ
s. This increases to once every 30
µ
s when
certain DRAM devices are used. (Controlled by the ram_fref bit in the
status registers.) RAS_ is asserted to both of Blocks A and B during each
of the 4 cycles. Along with RAS_, the Falcon pair also asserts CAS_ with
(OE_ then WE_) to one of the blocks during one of the four cycles. This
forms a read-modify-write which is a scrub cycle to that location.
After each of the 4 cycles, the DRAM row address increments by one.
When it reaches all 1’s, it rolls over and starts over at 0. Each time the row
address rolls over, the block that is scrubbed toggles between A and B.
Every second time that the row address rolls over, which of the 4 cycles
that is a scrub changes from 1st to 2nd, from 2nd to 3rd, from 3rd to 4th,
or from 4th to 1st. Every eighth time that the row address rolls over, the
column address increments by one. When the column address reaches all
1’s, it rolls over and starts over at 0. Each time the column address rolls
over, the
SC1, SC0 bits in the scrub/refresh register increment by one.
$X3FFFFF8
$7FFFFF
Upper
$X3FFFFF9
$7FFFFF
Upper
$X3FFFFFA
$7FFFFF
Upper
$X3FFFFFB
$7FFFFF
Upper
$X3FFFFFC
$7FFFFF
Lower
$X3FFFFFD
$7FFFFF
Lower
$X3FFFFFE
$7FFFFF
Lower
$X3FFFFFF
$7FFFFF
Lower
PowerPC 60x A0-A31
ROM/Flash A22-A0
ROM/Flash Device Selected
(Applies only when using two
32-bit Devices)
Summary of Contents for MVME2700 Series
Page 1: ...MVME2600 2700 Series Single Board Computer Programmer s Reference Guide V2600A PG2 ...
Page 13: ...xiv ...
Page 15: ...xvi ...
Page 67: ...1 50 Board Description and Memory Maps 1 ...
Page 151: ...2 84 Raven PCI Host Bridge Multi Processor Interrupt Controller Chip 2 ...
Page 215: ...3 64 Falcon ECC Memory Controller Chip Set 3 ...
Page 277: ...Glossary GL 14 G L O S S A R Y ...