Revision 1.02 – June 27, 2006
S5935 – PCI Product
Data Book
The PCI bus cycle address information is stored in the S5935 Pass-Thru Address Register.
Clock 0:
Clock 1:
The PCI address is recognized as a write to Pass-Thru region 1. The PCI data is stored in the S5935 Pass-Thru
Data Register. PTATN# is asserted to indicate a Pass-Thru access is occurring.
Pass-Thru status signals indicate what action is required by Add-On logic. Pass-Thru status outputs are valid
when PTATN# is active and are sampled by the Add-On at the rising edge of clock 2.
Clock 2:
PTBURST#
PTNUM[1:0]
PTWR
Deasserted. The access has a single data phase.
01. Indicates the PCI access is to Pass-Thru region 1.
Asserted. The Pass-Thru access is a write.
PTBE[3:0]#
0h. Indicates the Pass-Thru access is 32-bits.
SELECT#, address and byte enable inputs are driven to read the Pass-Thru Data Register at offset 2Ch.
DQ[31:0] are driven after RD# and SELECT# are asserted.
If PTRDY# is asserted at the rising edge of clock 3, PTATN# is immediately deasserted and the Pass-Thru
access is completed at clock 4.
Clock 3:
Clock 4:
If Add-On logic requires more time to read the Pass-Thru Data Register (slower memory or peripherals),
PTRDY# can be delayed, extending the cycle. With PTRDY# asserted at the rising edge of clock 4, PTATN# is
deasserted and the Pass-Thru access is completed at clock 5.
PTATN# and PTBURST# deasserted at the rising edge of clock 5 indicates the Pass-Thru access is complete.
The S5935 can accept new Pass-Thru accesses from the PCI bus at clock 6.
Clock 5:
Figure 2 shows a single cycle Pass-Thru write using
the Pass-Thru address information. This provides PCI
cycle address information to select a specific address
location within an Add-On memory or peripheral. Add-
On logic must latch the address for use during the data
transfer. Typically, the entire 32-bit address is not
required. The Add-On may implement a scheme
where only the required number of address bits are
latched. It may also be useful to use the Pass-Thru
region identifiers, PTNUM[1:0] as address lines. For
example, Pass-Thru region 1 might be a 64K block of
SRAM for data, while Pass-Thru region 2 might be
64K of SRAM for code storage (down-loaded from the
host during initialization). Using PTNUM0 as address
line A16 allows two unique Add-On memory regions to
be defined.
Figure 81. Single Cycle Pass-Thru Write with PTADR#
012345
BPCLK
6
PTATN#
PTBURST#
PTNUM[1:0]
PTWR
1
0h
PTBE[3:0]#
SELECT#
ADR[6:2]
BE[3:0]#
2Ch
0h
RD#
DQ[31:0]
PT ADDR PT DATA
PTRDY#
PTADR#
PCI Write cycle completed
154
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