MOTOROLA
Chapter 4. Processor Bus Interface
4-5
4.1.4 Processor Bus Interface Configuration Registers
Following system reset, initialization software must set up the programmable parameters
for the processor bus interface, located in processor interface configuration register 1 and 2
(PICR1 and PICR2). These programmable parameters control address and data bus
parking, enable recognition of local bus slaves, and determine the configuration of
multiprocessor systems and attached L2 caches, and sets the number of wait states required
until the AACK, ARTRY, and L2 HIT signals are sampled. See Section 3.2.7, “Processor
Interface Configuration Registers,” for more detail about programming the PICR1 and
PICR2 registers.
The following programmable parameters are relevant to the operation of the processor bus
interface:
PICR1[CF_L2_MP]. Sets the system for uniprocessor, L2 cache, or multiprocessor
configuration.
PICR1[CF_APARK]. The setting of this bit enables processor address bus parking
when the address bus is idle.
PICR1[CF_LOOP_SNOOP]. Setting this bit causes a PCI-to-memory transaction to
be repeated until it is not retried.
PICR1[CF_EXTERNAL_L2]. Setting this bit configures the system for external L2
cache.
PICR1[CF_DPARK]. When this bit is set the processor data bus is parked when the
data bus is idle.
PICR1[CF_LBA_EN]. The setting of this bit enables local bus slave bus accesses.
PICR1[CF_BREAD_WS]. These bits determine the minimum number of wait states
from TS to the first TA for burst reads.
PICR2[CF_APHASE_WS]. These bits determine the minimum number of wait
states for address phase of processor-initiated bus transactions.
PICR2[CF_L2_HIT_DELAY]. These bits determine the number of wait states from
assertion of TS until the HIT signal is valid.
PICR2[ABG_ADVANCE]. This bit controls address bus arbitration in
multiprocessor systems in situations where a processor-read-from-PCI operation
has been retried.
PICR2[CF_SNOOP_WS]. These bits determine the number of wait states until
ARTRY is sampled.