
2-16
MPC106 PCIB/MC User's Manual
MOTOROLA
Timing Comments
Assertion—Occurs when the current data beat can be completed.
Negation—Occurs after the clock cycle of the final (or only) data
beat of the transfer. For a burst transfer, TA may be negated between
beats to insert one or more wait states before the completion of the
next beat.
High-impedance—Occurs one-half clock cycle after negation.
2.2.2.14 Transfer Burst (TBST)
The transfer burst (TBST) signal is an input and output signal on the MPC106.
2.2.2.14.1 Transfer Burst (TBST)—Output
Following are the state meaning and timing comments for TBST as an output signal. Note
that all MPC106-generated snoop operations are 8-word bursts; therefore, TBST is always
asserted for snoop operations.
State Meaning
Asserted—Indicates that a burst transfer is in progress.
Negated—Indicates that a burst transfer is not in progress.
Timing Comments
Assertion/Negation—The same as A[0–31].
High-impedance—The same as A[0–31].
2.2.2.14.2 Transfer Burst (TBST)—Input
Following are the state meaning and timing comments for TBST as an input signal.
State Meaning
Asserted—Indicates that a burst transfer is in progress.
Negated—Indicates that a burst transfer is not in progress.
Timing Comments
Assertion/Negation—The same as A[0–31].
High-impedance—The same as A[0–31].
2.2.2.15 Transfer Error Acknowledge (TEA)—Output
The transfer error acknowledge (TEA) signal is an output on the MPC106. Note that the
TEA signal can be disabled by clearing the TEA_EN bit in processor interface
configuration register 1 (PICR1). Following are the state meaning and timing comments for
the TEA signal.
State Meaning
Asserted—Indicates that a bus error has occurred. Assertion of TEA
terminates the data transaction in progress; that is, it is not necessary
to assert TA because it is ignored by the target processor. An
unsupported transaction will cause the assertion of TEA (provided
TEA is enabled). Unsupported transactions include the following:
A direct-store access
A graphics read or write (
eciwx
or
ecowx
)
A write to the PCI interrupt acknowledge space
A write to Flash space, when Flash writes are disabled
An aborted processor-to-PCI transaction