EW31244SL7QV Datasheet, PDF (36/252 Pages) Intel Corporation – Intel® 31244 PCI-X to Serial ATA Controller

Intel^® 31244 PCI-X to Serial ATA Controller
Serial EEPROM
3.1.2
Table 13.
Figure 7.
READ Command
The EEPROM contains the downloadable programs needed in plug-in expansion card applications.
Normally, after the card is configured, the Host system downloads the program from the EEPROM
to RAM and executes from there.
Upon a ROM memory read, the GD31244 initiates an EEPROM READ operation at the memory
location addressed by the PCI bus. The PCI/PCI-X memory address is translated into the 17-bit
EEPROM memory address by the GD31244. Bits 23-17 of the EEPROM address are set to 0. Bits 16-0
of the EEPROM address are identical to the address on the PCI/PCI-X bus. The byte enables determine
how many bytes will be read from the EEPROM (1, 2 or 4). The byte enables on ROM memory reads is
presented in Table 13. The read memory (READ) operation for four bytes is shown in Figure 7.
Byte Enables on ROM Memory Reads
C/BE#3 C/BE#2 C/BE#1 C/BE#0 Length (Bytes) EEPROM A1 bit
1
1
1
0
1
0
1
1
0
1
1
0
1
0
1
1
1
1
0
1
1
1
1
1
1
1
0
0
2
0
0
0
1
1
2
1
0
0
0
0
4
0
NOTE: The access must be word aligned if 16-bit and dword aligned if 32-bit.
EEPROM A0 bit
0
1
0
1
0
0
0
Read Memory (READ) Operation, 4 Byte
SCS#
SCLK
SDO
0 4 8 12 16 20 24 28 32 36 40 44 48 52 54 56
00000011
23-bit Address
SDI
Hi -Z
Byte 0 Byte 1 Byte 2 Byte 3
76543210 76543210 76543210 76543210
Hi -Z
The READ command may only be issued when the EEPROM is ready to accept a new command.
When the device is busy, it cannot accept any new commands except RDSR.
To issue a READ command:
1. Issue a RDSR command to read that the RDY# bit is LOW in the EEPROM’s Status Register
to ensure that the EEPROM is ready to receive a new command.
2. When RDY# is not LOW, continue issuing RDSR commands until RDY# becomes LOW.
3. Issue the READ command by performing a byte, word or double word read of the ROM at the
desired address.
In PCs which are downloading the program stored in the EEPROM, the RDSR commands
mentioned above will NOT be issued prior to a Read. This is acceptable during normal operation
since the EEPROM will not be busy at this time.
When a READ command is issued while the EEPROM is busy, the EEPROM will return data
which is all zero.
36
April 2004
Developer’s Manual