Revision 1.02 – June 27, 2006
S5935 – PCI Product
INITIALIZATION
Data Book
host CPU to the S5935 produce PCI bus wait states
until one of the following events occurs:
All PCI bus agents and bridges are required to imple-
ment PCI Configuration Registers. When multiple PCI
devices are present, these registers must be unique to
each device in the system. The specified PCI proce-
dure for uniquely selecting a device’s configuration
space involves a dedicated signal, called IDSEL, con-
nected to each motherboard PCI bus device and PCI
slot.
•
The S5935 identifies that there is no valid boot
memory (and default Configuration Register
values are used).
•
The S5935 finishes downloading all configura-
tion information from a valid boot memory.
LOADING FROM BYTE-WIDE NV MEMO-
RIES
The host executes configuration cycles after reset to
each device on the PCI bus. The configuration regis-
ters provide information on PCI agent operation and
memory or I/O space requirements. These allow the
PCI BIOS to enable the device and locate it within sys-
tem memory or I/O space.
The SNV input on the S5935 indicates what type of
external boot-load device is present (if any). If SNV is
tied low, a byte-wide nv memory is assumed. In this
case, immediately after the PCI bus reset is deas-
serted, the address 0040h is presented on the nv
memory interface address bus EA[15:0]. Eight PCI
clocks later (240 ns at 33 MHz), data is read from the
nv memory data bus EQ[7:0] and address 0041h is
presented. After an additional eight PCI clocks, data is
again read from EQ7:0. If both accesses read are all
ones (FFh), it implies an illegal Vendor ID value, and
the external nv memory is not valid or not present. In
this situation, the AMCC default configuration values
are used.
After a PCI reset, the S5935 can be configured for a
specific application by downloading device setup infor-
mation from an external non-volatile memory into the
device Configuration Registers. The S5935 can also
be used in a default configuration, with no external
boot device.
When using a non-volatile boot memory to customize
operation, 64 bytes are required for S5935 setup infor-
mation. The rest of the boot device may be used to
implement an Expansion BIOS, if desired. Some of the
setup information is used to initialize the S5935 PCI
Configuration Registers, other information is not down-
loaded into registers, but is used to define S5935
operation (FIFO interface, Pass-Thru operation, etc.).
If either of the accesses to address 0040h and 0041h
contain zeros (not FFh), the next accesses are to loca-
tions 0050h, 0051h, 0052h, and 0053h. At these
locations, the data must be C0h (or C1h or C2h), FFh,
E8h, and 10h, respectively, for the external nv memory
to be valid. Once a valid external nv memory has been
recognized, it is read, sequentially, from location
0040h to 007Fh. The appropriate data is loaded into
the PCI Configuration Registers as described in Chap-
ter 4. Some of the boot device data is not downloaded
into Configuration Registers, but is used to enable fea-
tures and configure S5935 operation. Upon
completion of this procedure, the boot-load sequence
terminates and PCI configuration accesses to the
S5935 are acknowledged with the PCI Target Ready
(TRDY#) output.
PCI RESET
Immediately following the assertion of the PCI RST#
signal, the Add-On reset output SYSRST# is asserted.
Immediately following the deassertion of RST#,
SYSRST# is deasserted. The Add-On reset output
may be used to initialize state machines, reset Add-On
microprocessors, or reset other Add-On logic devices.
All S5935 Operation Registers and Configuration Reg-
isters are initialized to their default states at reset. The
default values for the Configuration Registers may be
overwritten with the contents of an external nv boot
memory during device initialization, allowing a custom
device configuration. Configuration accesses by the
Table 1 lists the required nv memory contents for a
valid configuration nv memory device.
92
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AMCC [ APPLIED MICRO CIRCUITS CORPORATION ]
