AT&T 3B2/300 Technical Reference Manual page 490

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CM 195U Equipped Device Table Data
The following table shows the Equipped Device Table (EDT) data for a STARLAN Interface card. A
value of O means NO; a value of 1 means YES. The indirect device (indir_dev) is only applicable to
systems equipped with Small Computer System Interface (SCSI). The request queue size (rq_size) and
the completion queue size (cq_size) are STARLAN software defined values. As such, the rq_size and
cq_size values may differ between versions of STARLAN software.
EDT ITEM DATA
IDENTIFICATION CODE (ID_code) Ox 0002
DEVICE NAME (dev_name) NI
REQUEST QUEUE SIZE (rq_size)
Ox DA
COMPLETION QUEUE SIZE (cq_size)
Ox 19
BOOT DEVICE (booLdev)
0
WORD SIZE (worcLsize) 1
BOARD SIZE (brcLsize)
0
SMART BOARD (smrLbrd)
1
CONSOLE CAPABILITY (cons_cap)
0
CONSOLE FILE (cons_file)
0
INDIRECT DEVICE (indir_dev)
0
Ethernet Data Packet Format
The format of an Ethernet Data Packet is as follows:
PREAMBLE
FIELD
PREAMBLE DESTINATION SOURCE TYPE DATA
CRC
ADDRESS ADDRESS
SIZE 64 BITS 48 BITS 48 BITS 16 BITS 46 TO 1500 BYTES 32 BITS
The Preamble is a 64-bit field of alternating l's and O's, ending with two
consecutive l's. This field synchronizes the receiving circuits to the incoming data
packet.
DESTINATION ADDRESS
The 48-bit Destination Address field is the nodal address to which the data is being
transmitted.
SOURCE ADDRESS
TYPE
DATA
CRC
The 48-bit Source Address field is the nodal address from which the data is being
transmitted.
The 16-bit Type field is used for a high-level data protocol.
The Data field is the data to be sent over the network and is from 46 to 1500 bytes
in length.
The 32-bit Cyclic Redundancy Check (CRC) field is calculated on all of the other
fields. This field is also called the Frame Check Sequence field.
FUNCTIONAL DESCRIPTION 3-237