s5920 Applied Micro Circuits Corporation (AMCC), s5920 Datasheet - Page 129

• Manufacturer Part Number: s5920
• Description: Pci Product
• Manufacturer: Applied Micro Circuits Corporation (AMCC)

S5920 – PCI Product: Pass-Thru Operation
Clock 3: The Add-On latches the address. Data 1 is
driven on the DQ bus as a result of the previous read.
As PTRDY# is sampled asserted, the PTBE# outputs
are updated to indicate which bytes are valid for the
second transfer. The BE[3:0]#, ADR[6:2], and
SELECT# inputs remain driven along with RD# to read
out the next data. PTRDY# remains asserted, indicat-
ing that the second transfer is complete.
Clock 4: Add-On logic uses the rising edge of this
clock to store DATA1. DATA2 is driven on the DQ bus
as a result of the previous read. As PTRDY# is sam-
pled asserted, the PTBE# outputs are updated to
indicate which bytes are valid for the third transfer.
PTRDY# remains asserted, indicating that the third
transfer is complete.
Clock 5: Add-On logic uses the rising edge of this
clock to store DATA2. PTBURST# is deasserted indi-
cating that only a single data phase remains. DATA3 is
driven on the Add-On bus. The PTBE# outputs are
updated to indicate which bytes are valid for the last
transfer. PTRDY# remains asserted, indicating that the
current transfer is complete.
Clock 6: Add-on logic uses the rising edge of this
clock to store DATA3 from the S5920. PTRDY# sam-
pled completes the last data phase. As a result, the
S5920 deasserts PTATN#, and drives DATA4 onto the
DQ bus. As the Add-on sampled PTBURST# deas-
serted and PTATN# asserted, it recognizes that the
previous read was the last one. As a result, the Add-
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On deasserts SELECT#, ADR[6:2], BE[3:0]#, RD# and
PTRDY#.
Clock 7: The Add-on logic stores DATA4 on the rising
edge of this clock. As PTATN# is deasserted, the
Pass-Thru access is complete, and the S5920 can
accept new Pass-Thru accesses starting on the next
clock. The other Pass-Thru signals can also change
state (in anticipation of a new transfer).
Figure 8 illustrates a Passive mode transfer with a
burst of five DWORDs in a PCI to Pass-Thru burst
write with PTRDY# used to insert wait states. In some
applications, Add-On logic may not be required to
transfer data on every ADCLK and can use PTRDY#
to control the data rate transfer. In this example, Add-
On logic latches data every other clock cycle. RD# is
shown deasserted when PTRDY# is deasserted, but
could remain active during the entire Add-On burst. In
this case, the DQ would not go to tri-state between
reads, and the PTBE# outputs would lose some of
their significance (as they would transition one cycle
early as a result of the “unused” read).
Clock 0: The address is recognized as a PCI write to
Pass-Thru region 0. The PCI bus write address is
stored in the Pass-Thru Address Register. The PCI
bus write data is stored in the S5920 write FIFO. Add-
On bus signals PTATN#, PTBURST#, PTNUM[1:0],
PTWR and PTBE[3:0] will update on the next rising
edge of ADCLK.
Revision 1.02 – April 12, 2007
Data Book
DS1596
129