lan91c100 Standard Microsystems Corp., lan91c100 Datasheet - Page 18

• Manufacturer Part Number: lan91c100
• Description: Feast ? Ast Ethernet Controller
• Manufacturer: Standard Microsystems Corp.

PACKET FORMAT IN BUFFER MEMORY
The packet format in memory is similar for the
Transmit and Receive areas. The first word is
STATUS WORD
BYTE COUNT
DATA AREA
CONTROL BYTE
2046 Max
(Decimal)
OFFSET
RAM
0
2
4
DATA STRUCTURES AND REGISTERS
FIGURE 4 – DATA PACKET FORMAT
bit 15
RESERVED
Written by CSMA upon transmit
completion (see Status
Register)
Written by CPU
Written/modified by CPU
Written by CPU to control
odd/even data bytes
CONTROL BYTE
TRANSMIT PACKET
STATUS WORD
18
DATA AREA
reserved for the status word, the next word is
used to specify the total number of bytes, and it
is followed by the data area.
holds the packet itself.
LAST DATA BYTE (if odd)
BYTE COUNT
Written by CSMA upon receive
completion (see RX Frame
Status Word)
Written by CSMA
Written by CSMA
Written by CSMA; also has
odd/even bit
RECEIVE PACKET
bit 0
The data area