Adaptec 1737100 Programmer Manual - Page 38
Total Packet Length, Buffer Length, Buffer Address
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AIC-6915 Ethernet LAN Controller Programmer's Manual s Total Packet Length: This 16-bit field defines the total packet length. If this field is zero, it is ignored and the total packet length is equal to the sum of all the buffers. If this field is nonzero, it is defined as the total packet length. Note: In Novell TCB/ECB blocks, the total packet length is not always equal to the sum of the buffer length. Transmit DMA pads extra bytes to the FIFO if the total packet length is greater than the sum of the buffer length. s Buffer Length: The length of the host buffer in bytes. s Buffer Address: The byte address of the host buffer. Type 1 (Generic), 32-bit Addressing Mode (Buffer Descriptor) In Type 1 and 2 buffer descriptors, the INTR, END, CALTCP, CRCEN, and Number of Tx Buffers fields are valid for the first buffer of a frame only. The ID, Length, and Address are valid for all buffers of the frame. The software driver must use the 'End' bit only in the first buffer descriptor of a frame. The queue wraps around after reading 8 bytes of descriptor data for Type 1 and 16 bytes of data for Type 2. Table 3-4. Type 1 Transmit DMA Descriptor (32-bit Addressing) 31 24 23 16 15 8 7 0 Skip Field (multiple of 8 bytes) One Skip Field per Buffer ID = 4'b1011 I E C C Number Of Tx Buffers N N A R (valid only if first T DL C fragment) R TE CN P Address Length (bytes) Type 2 (Generic), 64-bit Addressing Mode (Buffer Descriptor) In Type 1 and 2 buffer descriptors, the INTR, END, CALTCP, CRCEN, and Number of Tx Buffers fields are valid for the first buffer of a frame only. The ID, Length, and Address are valid for all buffers of the frame. The software driver must use the 'END' bit only in the first buffer descriptor of a frame. The queue wraps around after reading 8 bytes of descriptor data for Type 1 and 16 bytes of data for Type 2. 3-8
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