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MPC7400 RISC Microprocessor Users Manual
MPX Bus Signal ConTguration
8.4.4.8.2 Cache Inhibit (CI)Input
The cache inhibit (CI) signal is an input signal on the MPC7400. Following are the state
meaning and timing comments for the CI signal as an input in MPX bus mode.
State Meaning
AssertedIndicates that the MPC7400 should not assert HIT to
provide data intervention in response to a snoop because data
intervention is not allowed for cache-inhibited accesses.
NegatedIndicates that the MPC7400 may assert HIT to provide
data intervention in response to a snoop, provided WT is not asserted
Timing Comments
Assertion/NegationThe same as A[0:31]
8.4.5 MPX Address Transfer Termination Signals
The address transfer termination signal functions in MPX bus mode are very similar to that
of 60x bus mode, with the exceptions noted in the following subsections. For detailed
information about how these signals interact, see Section 9.6.1.4, òAddress Termination
Phase in MPX Bus Mode.ó
8.4.5.1 Address Acknowledge (AACK)Input
The address acknowledge (AACK) signal is an input signal on the MPC7400. Following
are the state meaning and timing comments for the AACK signal in MPX bus mode.
State Meaning
AssertedThe same as 60x bus interface except the MPC7400, as
address bus master, does not release the address and transfer attribute
signals to high impedance in response to AACK when the following
conditions are met:
¥
Address bus driven mode is enabled (MSSCR0[ABD] = 1) and
there was a BG to the MPC7400 on the previous clock cycle.
¥
Address bus streaming is occurring and the MPC7400 qualiTed
a BG in the previous clock cycle.
NegatedSame as 60x bus interface
Timing Comments
AssertionThe same as 60x bus interface except that because
AACK is not in the qualiTed bus grant equation and a synthesized
ABB is not generated in MPX bus mode, the bus arbiter must negate
BG in every cycle the arbiter is delaying AACK to prevent a qualiTed
bus grant in those cases.
NegationSame as 60x bus interface
8.4.5.2 Address Retry (ARTRY)
The address retry (ARTRY) signal is both an input and output signal on the MPC7400 in
MPX bus mode.