
Chapter 8. Signal Descriptions
8-29
MPX Bus Signal ConTguration
8.4.3.4 Address Parity (AP[0:3])Input
Following are the state meaning and timing comments for the AP[0:3] input signals on the
MPC7400.
State Meaning
Asserted/NegatedSame as A[0:31]
Timing Comments
Assertion/NegationSame as A[0:31]
8.4.4 Address Transfer Attribute Signals in MPX Bus Mode
The transfer attribute signal functions in MPX bus mode are very similar to that of 60x bus
mode, with the exceptions noted in the following subsections.
8.4.4.1 Transfer Start (TS)Output
Following are the state meaning and timing comments for the transfer start TS output signal
on the MPC7400.
State Meaning
Asserted
Same as 60x bus interface
Negated
Same as 60x bus interface
Timing Comments
AssertionSame as 60x bus interface
NegationSame as 60x bus interface
High ImpedanceOccurs two bus clock cycles after TS is asserted,
unless address bus streaming is occurring and the MPC7400
qualiTed a BG on the previous cycle.
8.4.4.2 Transfer Start (TS)Input
Following are the state meaning and timing comments for the transfer start TS input signal
on the MPC7400.
State Meaning
Asserted
Same as 60x bus interface
NegatedSame as 60x bus interface
Timing Comments
Assertion
Can occur on any bus clock cycle following a qualiTed
BG that is accepted by the processor.
Negation Must occur one bus clock cycle after assertion.
8.4.4.3 Transfer Type (TT[0:4])
The transfer type (TT[0:4]) signals consist of Tve input/output signals on the MPC7400.
8.4.4.3.1
Transfer Type (TT[0:4])
Output
Following are the state meaning and timing comments for the transfer type TT[0:4] output
signals on the MPC7400 in MPX bus mode. Note that there is a new transfer type called
read claim (RCLAIM; TT[0:4] = 0b0111) deTned for MPX bus mode that is used for
accesses generated by touch-for-store instructions.