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Falcon ECC Memory Controller Chip Set
3
If so enabled, single- and double-bit scrub errors are logged, and the
PowerPC 60x bus master is notified via interrupt.
Chip Defaults
Some jumper option kinds of parameters need to be configured by
software in the Falcon pair. These parameters include DRAM and
ROM/Flash attributes. In order to set up these parameters correctly,
software needs some way of knowing about the devices that are being used
with the Falcon pair. One way of providing this information is by using the
power-up status registers in the Falcon pair. At power-up reset, each
Falcon latches the level on its RD0-RD63 signal pins into its power-up
status registers. Since the RD signal pins are high impedance during reset,
their power-up reset level can be controlled by pullup/pulldown resistors.
(They are pulled-up internally.)
External Register Set
Each chip in the Falcon pair has an external register chip select pin which
enables it to talk to an external set of registers. This interface is like the
ROM/Flash interface but with less flexibility. It is intended for the system
designer to be able to implement general-purpose status/control signals
with this external set. Refer to the
for a description
of this register set.
CSR Accesses
An important part of the operation of a Falcon pair is that the value written
to the internal control registers and SRAM in each of the two chips must
be the same at all times. In order to facilitate this, writes to the pair itself
are restricted to the upper Falcon only. When software writes to the upper
Falcon, hardware in the two chips shifts this same value into the lower
Falcon before the cycle completion is acknowledged. The shifting is done
in holding registers such that the actual update of the control register
happens on the same CLOCK cycle in both chips. Writes to the upper
Falcon can be single-byte or 4-byte. Writes to the lower Falcon are
ignored.