One Stop Systems, Inc. OSS-wanPCI-CxT1E1 User Manual
Rev. A
7
Memory Map
The Expansion Bus (EBus) that carries the data on the OSS-wanPCI-CxT1E1 is connected to six byte-wide devices. These devices
are the four COMETs, the serial EEPROM, and the iSPLD. The EBus interface uses the lower 20 bits from the PCI address line
(AD[19:0]) to construct a byte address for the EBus. Specifically, PCI address lines AD[19:2] are remapped to EBus address lines
EAD[17:0].
Only single D-word (32-bit) PCI operations can be performed when accessing the EBus. Please refer to the N8474/CN8474A
specification for more detail. All EBus accesses are on the least significant byte of the PCI bus and are aligned on the 32-bit
boundary.
Serial EEPROM
Board serial numbers are stored in a Microchip 93LC46A and packaged in a small outline integrated circuit. This device can hold
1024 bits organized in a 128x8 format. The PCI host reads and writes to this device in a bit serial fashion
.
InstructionSB SB
OP
code
EEPROM address bits
Data IN
Data OUT
# CLK
cycles
Erase
1
11
A6
A5 A4 A3 A2 A1 A0
--
RDY_/BSY
10
Erase All
1
0
1
0
X
X
X
X
X
--
RDY_/BSY
10
Disable
Erase/Write
1
0
0
0
X
X
X
X
X
--
HIGH-Z
10
Enable
Erase/Write
1
0
1
1
X
X
X
X
X
--
HIGH-Z
10
Read
1
10
A6
A5 A4 A3 A2 A1 A0
--
D7-D0
18
Write
1
1
A6
A5 A4 A3 A2 A1 A0 D7-D0
RDY_/BSY
18
Write All
1
0
0
1
X
X
X
X
X
D7-D0
RDY_/BSY
18
Extended address bit definitions
Note:
Insert a 500ns delay between each bit/write operation
Device PCIAddress
COMET 1
xxx80000 Hex
COMET 2
xxx90000 Hex
COMET 3
xxxA0000 Hex
COMET 4
xxxB0000 Hex
SERIAL
EEPROM
xxxC0000 Hex
iSPLD
xxxD0000 Hex
Data Bit
Description
0 Data
Out
1 Data
In
2 Chip
Select
