
Chapter 2. Signal Descriptions
2-19
2.5.3 Address Retry (ARTRY)—Input
Following are state and timing descriptions for ARTRY as an input signal.
State Meaning
Asserted—For the address bus master, ARTRY indicates the device
must retry the preceding address tenure and immediately negate BR
(if asserted). If the associated data tenure has begun, the 603 and 604
also abort the data tenure immediately even if burst data has been
received. For devices that are not the address bus master, this input
indicates they should immediately negate BR for one bus clock cycle
after the assertion of ARTRY by the snooping bus master to allow a
write-back operation.
Negated/High Impedance—The master need not retry the last
address tenure.
Timing Comments
Assertion—May occur as soon as the second cycle after TS or XATS
is asserted; must occur by the bus clock cycle immediately after the
assertion of AACK if an address retry is required.
Negation—Must occur in the second cycle after AACK is asserted.
2.5.4 Shared (SHD)—Output
Following are state and timing descriptions for the shared (SHD) as an output signal.
State Meaning
Asserted—If ARTRY is negated, indicates that after this transaction
completes successfully, the master will keep a valid shared copy of
the address or that a reservation exists on this address. If SHD and
ARTRY are asserted for a snooping master, the snoop hit modified
data that will be pushed as the master’s next address transaction.
Negated/High Impedance—After this address is transferred, the
processor will not have a valid copy of the snooped address.
Timing Comments
Assertion/Negation—Same as ARTRY.
High Impedance—Same as ARTRY.
Because it does not support the shared MESI state (S), the 603 does not implement SHD.
2.5.5 Shared (SHD)—Input
Following are state and timing descriptions for SHD as an input signal.
State Meaning
Asserted—If ARTRY is not asserted, the master must allocate the
incoming cache block as shared (S) for a self-generated transaction.
Applies only to read and read atomic transactions.
Negated—If ARTRY is negated, the master can allocate the
incoming cache block as exclusive (E) for a self-generated read or
read-atomic transaction.
Timing Comments
Assertion/Negation—The same as ARTRY.
Because it does not support the shared (S) MESI state, the 603 does not implement SHD.