
IBM2520L8767
IBM Processor for ATM Resources
Packet Header
Page 48 of 553
atmrm.chapt03.01
08/27/99
buffer_offset
This field contains the offset into the buffer that the transmit data starts.
enable_blocking #
When set, this bit enables OAM blocking cells to be sent on the associated VC by the segmentation
logic. Other fields in the LCD define the content and frequency of these frames. Setting this bit also
forces statistics to be kept for the associated LCD regardless of the state of the enable_statistics bit.
This same function can be globally controlled in the SEGBF control register.
enable_statistics #
When set, this bit enables statistics keeping for the associated LCD. Another eight bytes of the associ-
ated LCD is used to maintain counts of the total number of user cells and the total number of user cells
with CLP=0 that have been sent over this VC. This same function can be globally controlled in the
SEGBF control register.
flush_LCD #
When set, this bit causes the segmentation logic to flush all frames currently queued to the LCD without
performing any segmentation on them.
generate_CRC10 #
This bit is set if the header of the currently transmitted packet has specified that the cells in this packet
should have CRC-10 generated. When set, this bit overrides the other AAL select bits in the LCD and
forces the segmentation logic to generate a CRC-10 terminated cell. In this mode, the segmentation
logic fetches 52 bytes of data from memory. The HEC is calculated over the first four bytes fetched,
and appended following these four bytes. The next 48 bytes are used to calculate the CRC-10 and the
zero-padded two-byte result is appended after the 48 bytes of data. This function is intended to make it
easier to send OAM cells.
OAM_CLP_source #
When reset, the CLP bit for all OAM cells is retrieved from the ATM header in the LCD. When set, the
CLP bit for all OAM cells is retrieved from the OAM_CLP_value field in the LCD. This allows OAM traf-
fic to be sent with a different CLP value than other traffic on the VC.
ABR Code Variables Definitions
(Page 3 of 7)
Field Name
Field Description