lan91c95 Standard Microsystems Corp., lan91c95 Datasheet - Page 29

• Manufacturer Part Number: lan91c95
• Description: Isa/pcmcia Full Duplex Single-chip Ethernet And Modem Controller With Ram
• 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 reserved for the status word, the next word is
1 5 3 6 M a x
( D E C I M A L )
O F F S E T
R A M
CONTROL BYTE
STATUS WORD
0
2
4
BYTE COUNT
DATA AREA
bit15
R E S E R V E D
C O N T R O L B Y T E
FIGURE 8 - DATA PACKET FORMAT
Written by CSMA upon transmit
completion (see Status
Register)
Written by CPU
Written by CPU
Written by CPU to control
ODD/EVEN data bytes
TRANSMIT PACKET
S TAT U S W O R D
29
DATA AREA
B Y T E C O U N T ( a lways even)
used to specify the total number of bytes, and
that in turn is followed by the data area. The
data area holds the packet itself, and its length
is determined by the byte count. The packet
memory format is word oriented.
L A S T D ATA BYTE (if odd)
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
bit0