Address Retry; Shared (Shd); Shared (Shd)-Output - IBM PowerPC 604 User Manual

• 3:1 bus ratio-high-impedance for 1/3 bus clock cycle, deasserted
for 'l/3 bus clock cycle, then high-impedance.
• 3:2 bus ratio-high-impedance for 1/3 system clock cycle,
deasserted for 1 bus clock cycle, then high-impedance.
This special method of negation may be disabled by setting the
disable snoop response high state restore bit (bit 7) in HIDO.
7.2.5.2.2 Address Retry (ARTRY)-lnput
Following are the state meaning and timing comments for the ARTRY input signal.
State Meaning
Asserted-If the 604 is the address bus master, ARTRY indicates
that the 604 must retry the preceding address tenure and immediately
negate BR (if asserted). If the associated data tenure has already
started, the 604 will also abort the data tenure immediately, even if
the burst data has been received. If the 604 is not the address bus
master, this input indicates that the 604 should immediately negate
BR for one bus clock cycle following the assertion of ARTRY by the
snooping bus master to allow an opportunity for a copy-back
operation
to
main memory. Note that the subsequent address
presented on the address bus may not be the same one associated
with the assertion of the ARTRY signal.
Timing Comments
Negated/High Impedance-Indicates that the 604 does not need to
retry the last address tenure.
Assertion-May occur as early as the second cycle following the
assertion of TS or XATS, and must occur by the bus clock cycle
immediately following the assertion of AACK if an address retry is
required.
Negation-Must occur during the second cycle after the assertion of
AACK.
7 .2.5.3 Shared (SHD)
The shared (SHD) signal is both an input and output signal on the 604.
7.2.5.3.1 Shared (SHD)-Output
Following are the state meaning and timing comments for the SHD output signal.
State Meaning
Asserted-Indicates that the 604 had a cache hit on a shared block,
or, if asserted with ARTRY, a snoop push of modified data is
required.
Negated/High Impedance-Indicates that the 604 did not have a
cache hit on the snooped address.
-:"'-=:==
Timing Comments
Assertion/Negation-Same as ARTRY.
High Impedance-Same as ARTRY.
Chapter 7. Signal Descriptions
7-17