
Applied Micro Circuits Corporation
6195 Lusk Blvd., San Diego, CA 92121 (619) 450-9333
8-11
PCI CONTROLLER
S5933
DEVICE SPECIFICATION
8.1.5.2 Target Requested Retries
When the S5933 FIFO registers are accessed
(S5933 as a target) and data is unavailable (empty
FIFO) for read transfers or cannot be accepted for
write transfers (full FIFO), the S5933 immediately ter-
minates the cycle by requesting a retry. The S5933
also initiates a retry for Pass-Thru writes where the
Add-On has not completed the preceding Pass-Thru
write by asserting PTRDY#, and for Pass-Thru reads
where the Add-On cannot supply data within 8 PCI
clocks (16 clocks for the first data phase of a burst).
A retry is requested by a target asserting both
STOP# and DEVSEL# while TRDY# is deasserted.
Figure 8-11 shows the behavior of the S5933 when
performing a target-initiated retry.
8.1.5.3 Target Aborts
A target abort termination represents an error condi-
tion where no number of retries will produce a suc-
cessful target access. A target abort is uniquely
identified by the target deasserting DEVSEL# and
TRDY# while STOP# is asserted. When a target per-
forms an abort, it must also set bit 11 of its PCI
Status register (Section 4.4). The S5933 configura-
tion and operation registers never respond with a tar-
get abort when accessed. If the S5933 encounters
this condition when operating as a PCI initiator, the
S5933 sets bit 12 (received target abort) in the PCI
Status register. Figure 8-12 depicts a target abort
cycle.
Target termination types are summarized in Table 8-2.
Termination
DEVSEL#
STOP# TRDY#
Comment
Disconnect
on
Data is transferred. Transaction needs to be re-initiated
to complete.
Retry
on
off
Data was not transferred.
Transaction should be tried later.
Abort
off
on
off
Data was not transferred. Fatal error.
Table 8-2. Target Termination Types
Figure 8-11. Target-Initiated Retry
PCI CLOCK
FRAME #
IRDY#
TRDY#
STOP#
DEVSEL#
1
2
3
INITIATOR
SEQUENCES IRDY#
+ FRAME# TO RETURN
TO IDLE STATE
45
TARGET
RETRY
SIGNALED
(T)
(I)
(I) = DRIVEN BY INITIATOR
(T) = DRIVEN BY TARGET