User Manual
BCM1250/BCM1125/BCM1125H
10/21/02
B r o a d c o m C o r p o r a t i o n
Document
1250_1125-UM100CB-R
Section 6: DRAM Page
105
Figure 14: Memory Controller Block Diagram
Entries are selected for issue from the RQQ based on the state of the other entries and the status returned by
the memory pipeline controller for each of the channels. The issues can be out-of-order, and use the following
rules:
•
Any access to configuration registers causes serialization of the queue. These accesses can be in
progress for some time (40-50 ZBbus clocks), so should not be done during normal operation.
•
Any access with address conflict with an entry already in the queue will be only issued when it reaches the
head of the queue. (It can be bypassed by other requests).
•
If priority is enabled in the
mc_config_1
register, any read requests from I/O bridge 1 are given priority
and are issued in-order. If a read request conflicts with an existing write, the write is also given priority.
•
If a channel is currently doing a read, all reads to that channel will be issued ahead of any writes.
•
If a read has been bypassed enough times to reach its age_limit (see below) it will go ahead of other
reads.
•
If a channel is currently doing a write, all writes to that channel will be issued ahead of any reads up to a
maximum number of consecutive writes that are set in the channel configuration register.
•
If the open page policy is being used an entry that hits on an open page goes first.
•
If the open page policy is disabled an entry that is to a precharged bank (closed bank) goes first.
•
If a channel is currently idle, reads will be issued before writes.
•
Otherwise entries are issued in the order they were allocated.
RQQ
Request Queue
DBF
Data Buffer
M-channel1
Control
M-channel0
Control
ZBbus
M-channel1
M-channel0
address/cmd
write-data
read-data
Addr/cmd
BCM1250 Only
Содержание BCM1125
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