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Falcon ECC Memory Controller Chip Set
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logging the error, that Falcon also pulses its DPERR_ signal true for the
duration of one clock period, two clock periods after the TA_ during which
the error data is captured.
While normal (default) operation is for the Falcon to check data parity only
on writes to itself, it can also be programmed to check data parity on all
reads or writes to any device on the 60x bus
Cache Coherency
The Falcon supports cache coherency to DRAM only. It does this by
monitoring the ARTRY_ control signal on the PowerPC 60x bus and
behaving appropriately when it is asserted. When ARTRY_ is asserted, if
the access is a DRAM read, the Falcon does not source the data for that
access. If the access is a DRAM write, the Falcon does not write the data
for that access. Depending upon when the retry occurs, the Falcon may
cycle the DRAM even though the data transfer does not happen.
Cache Coherency Restrictions
The PowerPC 60x GBL_ signal must not be asserted in the CSR areas.
L2 Cache Support
The Falcon pair provides support for a look-aside L2 cache by
implementing a hold-off input, L2CLM_. On cycles that select the Falcon
pair, the Falcon pair samples L2CLM_ on the second rising edge of
CLOCK after the assertion of TS_. If L2CLM_ is high, the Falcon pair
responds normally to the cycle. If it is low, the Falcon pair ignores the
cycle.
ECC
The Falcon pair performs single-bit error correction and double-bit error
detection for DRAM. (No checking is provided for ROM /Flash.) The 64-
bit wide PowerPC 60x data bus is divided into upper (DH0-DH31) and
lower (DL0-DL31) halves. Each half is routed through a Falcon which