OX9162
OXFORD SEMICONDUCTOR LTD.
7
SERIAL EEPROM
7.1 Specification
7.2 EEPROM Data Organisation
The OX9162 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 also allows configuration accesses
to the local bus (or parallel port), which can be useful for
default set ups.
The serial EEPROM data is divided in five 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 OX9162 registers from the serial
EEPROM. The general EEPROM data structure is shown
in Table 8.
The EEPROM interface is based on the 93C46/56 serial
EEPROM devices which have a proprietary serial interface
known as MicrowireTM. 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).
DATA Size (Words) Description
Zone
0
1
2
3
4
One
Header
One or more
One to four
Two or more
Multiples of 2
Local Configuration Registers
Identification Registers
PCI Configuration Registers
Function Access
Table 8: EEPROM data format
7.2.1 Zone0: Header
The OX9162 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. NOTE: that
any attempted PCI access while data is being downloaded
from the serial EEPROM will result in a retry. 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 header identifies the EEPROM program as valid.
Bits Description
15:4 These bits should return 0x840 to identify a valid
program. Once the OX9162 reads 0x840 from
these bits, it sets LCC[28] to indicate that a valid
EEPROM program is present.
3
2
1
0
1 = Zone1 (Local Configuration) exists
0 = Zone1 does not exist
1 = Zone2 (Identification) exists
0 = Zone2 does not exist
1 = Zone3 (PCI Configuration) exists
0 = Zone3 does not exist
1 = Zone4 (Function Access) exists
0 = Zone4 does not exist
Note that 93C46 and 93C56 EEPROM devices offer 128
and 256 bytes of programmable data respectively.
A WindowsÒ based utility to program the EEPROM is
available. For further details please contact Oxford
Semiconductor (see back cover).
The programming data for each zone follows the
proceeding zone if it exists. For example a Header value of
0x840F indicates that all zones exist and they follow one
another in sequence, while 0x8405 indicates that only
Zones 2 and 4 exist where the header data is followed by
Zone2 WORDs, and since Zone3 is missing Zone2
WORDs are followed by Zone4 WORDs.
MicrowireTM is a trade mark of National Semiconductor. For
a description of MicrowireTM, please refer to National
Semiconductor data manuals.
Data Sheet Revision 1.1 PRELIMINARY
Page 25
OXFORD [ OXFORD SEMICONDUCTOR ]
