OX9160 Datasheet, PDF (25/38 Pages) Oxford Semiconductor – PCI Peripheral Bridge with EPP Parallel Port & 8/32 bit local bus

OXFORD SEMICONDUCTOR LTD.
7 SERIAL EEPROM
7.1 Specification
The OX9160 can be configured using an optional serial
Electrically-Erasable Programmable Read Only Memory
(EEPROM). If the EEPROM is not present, the device will
remain in its default configuration after reset. Although this
may be adequate for some applications, many will benefit
from the degree of programmability afforded by this
feature.
The EEPROM interface is based on the 93C46/56 serial
EEPROM devices which have a proprietary serial interface
known as Microwire^TM. The interface has four pins which
supply the memory device with a clock, a chip-select, and
serial data input and output lines. In order to read from
such a device, a controller has to output serially a read
command and address, then input serially the data. The
93C46/56 and compatible devices have a 16-bit data word
format but differ in memory size (and number of address
bits).
The OX9160 incorporates a controller module which reads
data from the serial EEPROM and writes data into the
configuration register space. It performs this operation in a
sequence which starts immediately after a PCI bus reset
and ends either when the controller finds no EEPROM is
present or when it reaches the end of its data. The
operation of this controller is described below. Following
device configuration, driver software can access the serial
EEPROM through four bits in the device-specific Local
Configuration Register LCC[27:24]. Software can use this
register to manipulate the device pins in order to read and
modify the EEPROM contents.
The OX9160 requires a total of bytes of EEPROM data to
program all the EEPROM writable registers. The 93C46
and 93C56 EEPROM devices offer 128 and 256 bytes of
programmable data respectively.
A Windows® based utility to program the EEPROM is
available. For further details please contact Oxford
Semiconductor (see back cover).
Microwire^TM is a trade mark of National Semiconductor. For
a description of MicroWire, please refer to National
Semiconductor data manuals.
OX9160
7.2 EEPROM Data Organisation
The serial EEPROM data is divided in four zones. The size
of each zone is an exact multiple of 16-bit WORDs. Zone0
is allocated to the header. A valid EEPROM program must
contain a header. The EEPROM can be programmed from
the PCI bus. Once the programming is complete, the
device driver should either reset the PCI bus or set
LCC[29] to reload the OX9160 registers from the serial
EEPROM. The general EEPROM data structure is shown
in Table 10.
DATA
Zone
0
1
2
3
Size (Words) Description
One
One or more
Two
Two or more
Header
Local Configuration Registers
Identification Registers
PCI Configuration Registers
Table 10: EEPROM data format
7.2.1 Zone0: Header
The header identifies the EEPROM program as valid.
Bits Description
15:4 These bits should return 0x950 to identify a valid
program. Once the OX9160 reads 0x950 from
these bits, it sets LCC[28] to indicate that a valid
EEPROM program is present.
3 Reserved. Write ‘0’ to this bit.
2 1 = Zone1 (Local Configuration) exists
0 = Zone1 does not exist
1 1 = Zone2 (Identification) exists
0 = Zone2 does not exist
0 1 = Zone3 (PCI Configuration) exists
0 = Zone3 does not exist
The programming data for each zone follows the
proceeding zone if it exists. For example a Header value of
0x9507 indicates that all zones exist and they follow one
another in sequence, while 0x9505 indicates that only
Zones 1 and 3 exist where the header data is followed by
Zone1 WORDs, and since Zone2 is missing Zone1
WORDs are followed by Zone3 WORDs.
Data Sheet Revision 1.22
Page 25