Technical information

3-6
AIC-6915 Ethernet LAN Controller Programmer’s Manual
■
ID
: 4 bits. This field is used by the software/debugger to identify the start of a
descriptor. If a transmit DMA operation does not see a matched ID in this field, it
aborts the DMA operation and sets an interrupt status bit.
■
Number of Fragments
: 8 bits. Defines the number of follow-on segments. This field
must be “nonzero”.
■
END
: Indicates that the current descriptor is at the end of the queue. The ‘End” has
different functionality for the following conditions:
Table 3-1. Type 0 Transmit DMA Descriptor (32-bit Addressing Only)
31 24 32 16 15 8 7 0
Skip Field (multiple of 8 bytes)
One Skip Field per Packet
ID =
4’b1011
I
N
T
R
E
N
D
C
A
L
T
C
P
C
R
C
E
N
Reserved Reserved
Reserved Number Of Tx Buffers
First Buffer Address
Total Packet Length First Buffer Length
Last Buffer Address
Reserved Last Buffer Length