Data Parity Error (Dpe)-Output; Data Bus Disable; Data Transfer Termination Signals - IBM PowerPC 604 User Manual

Timing Comments Assertion/Negation-The same as DLO-DL31.
7 .2. 7 .3 Data Parity Error (DPE)-Output
The data parity error (DPE) signal is an output signal (output-only) on the 604. Note that
the (DPE) signal is an open-drain
type
output, and requires an external pull-up resistor (for
example, 10
kn
to
V dd) to assure proper deassertion of the (DPE) signal. Following are the
state meaning and timing comments for the DPE signal.
State Meaning Asserted-Indicates incorrect data bus parity.
Negated-Indicates correct data bus parity.
Timing Comments Assertion-Occurs on the second bus clock cycle after TA is
asserted to the 604.
High Impedance-Occurs on the third bus clock cycle after TA is
asserted to the 604.
7 .2. 7 .4 Data Bus Disable (DBDIS)-lnput
The Data Bus Disable (DBDIS) signal is an input signal (input-only) on the 604. Following
are the state meanings and timing comments for the DBDIS signal.
State Meaning Asserted-Indicates (for a write transaction) that the 604 must
release data bus and the data bus parity to high impedance during the
following cycle. The data tenure will remain active, DBB will
remain driven, and the transfer termination signals will still be
monitored by the 604.
Negated-Indicates the data bus should remain normally driven.
DBDIS is ignored during read transactions.
1iming Comments Assertion/Negation-May be asserted on any clock cycle when the
604 is driving, or will be driving the data bus; may remain asserted
multiple cycles.
7 .2.8 Data Transfer Termination Signals
Data termination signals are required after each data beat in a data transfer. Note that
in
a
single-beat transaction, the data termination signals also indicate the end of the tenure,
while in burst accesses, the data termination signals apply to individual beats and indicate
the end of the tenure only after the final data beat.
For a detailed description of how these signals interact, see Section 8.4.4, "Data Transfer
Termination."
7-22 PowerPC 604 RISC MicroproC888or User's Manual