Revision 5.03 – June 14, 2006
S5320 – PCI Match Maker: PCI Bus Protocol
Data Sheet
Figure 45. Burst PCI Bus Read Attempt to S5320 Reg-
isters or Expansion ROM
Target Disconnects
There are many situations where a target may discon-
nect. Slow responding targets may disconnect to
permit more efficient (faster) devices to be accessed
while they prepare for the next data phase. Or a target
may disconnect if it recognizes that the next data
phase in a burst transfer is out of its address range. A
target disconnects by asserting STOP#, TRDY#, and
DEVSEL# as shown in Figures 47 and 48. The initiator
in Figure 47 responds to the disconnect condition by
deasserting FRAME# on the following clock but does
not complete the data transfer until IRDY# is asserted.
The timing diagram in Figure 48 also applies to the
S5320.
1
2
3
4
5
PCLK
FRAME#
AD[31:0]
C/BE[3:0]#
IRDY#
(T)
(I)
Address
Data
Bus
Cmd
Byte
Enables
TRDY#
DEVSEL#
STOP#
The S5320 performs a target disconnect if a burst
access is attempted to any of its PCI Operation/Con-
figuration Registers, or to the Expansion ROM.
Target Requested Retries
(I) Driven by Initiator
(T) Driven by Target
The S5320 initiates a retry for Pass-Thru writes when
the Write FIFO is full, and for Pass-Thru reads when
the Add-On cannot supply data within 16 PCI clocks
from the assertion of FRAME# (for the first data phase
of a burst). A retry is requested by a target by assert-
ing both STOP# and DEVSEL# while TRDY# is
deasserted. Figure 49 shows the behavior of the
S5320 when performing a target-initiated retry.
Figure 46. Burst PCI Bus Write of S5320 Registers
1
2
3
4
5
PCLK
(I)
(I)
FRAME#
AD[31:0]
C/BE[3:0]#
IRDY#
Figure 47. Target Disconnect Example 1
Address
Data 1
BE 1
Data 2
1
2
3
4
5
Bus
Cmd
BE 2
(I)
(I)
PCLK
(I)
FRAME#
IRDY#
(T)
(T)
(T)
TRDY#
DEVSEL#
STOP#
(I)
(T)
(T)
(T)
TRDY#
DEVSEL#
STOP#
Data
Transfered
(I) Driven by Initiator
(T) Driven by Target
No Data
Transfered
(I) Driven by Initiator
(T) Driven by Target
Target
Disconnect
Identified
Target-Initiated Termination
Data
Transfered
There are situations where the target may end a trans-
fer prematurely. This is called “target-initiated
termination.” Target termination falls into three catego-
ries: disconnect, retry, and target abort. Only the
disconnect termination completes a data transfer.
94
DS1656
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