
System Memory Controller (SMC)
MVME5100 Single Board Computer Programmer’s Reference (6806800H17B)
197
3.2.3.2
Completing Data Transfers
If an address transfer to the SMC will have an associated data transfer, the SMC begins a read or
write cycle to the accessed entity (SDRAM/ROM/Flash/Internal or External Register) as soon as
the entity is free. If the data transfer will be a read, the SMC begins providing data to the PPC60x
bus as soon as the entity has data ready and the PPC60x data bus is granted. If the data transfer
will be a write, the SMC begins latching data from the PowerPC data bus as soon as any
previously latched data is no longer needed and the PPC60x data bus is available.
3.2.3.3
PPC60x Data Parity
The Hawk has 8 DP pins for generating and checking PPC60x data bus parity.
During read cycles that access the SMC, the Hawk generates the correct value on DP0-DP7 so
that each data byte lane along with its corresponding DP signal has odd parity. This can be
changed on a lane basis to even parity by software bits that can force the generation of wrong
(even) parity.
During write cycles to the SMC, the SMC checks each of the eight PPC60x data byte lanes and
its corresponding DP signal for odd parity. If any of the eight lanes has even parity, the SMC logs
the error in the CSR and can generate a machine check if so enabled.
While normal (default) operation is for the SMC to check data parity only on writes to it, it can
be programmed to check data parity on all reads or writes to any device on the PPC bus.
Data Parity Error Log Register
for additional control register details.
3.2.3.4
PPC60x Address Parity
The Hawk has four AP pins for generating and checking PPC60x address bus parity.
During any address transfer cycle on the PPC60x, the SMC checks each of the four 8-bit PPC60x
address lanes and its corresponding AP signal for odd parity. If any of the four lanes has even
parity, the SMC logs the error in the CSR and can generate a machine check if so enabled.
Note that the SMC does not generate address parity because it is not a PPC60x address master.
Address Parity Error Log Register
for additional control register details.
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