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IBM3206K0424
IBM Processor for Network Resources
Preliminary
Packet Header
Page 76 of 676
pnr25.chapt03.01
August 14, 2000
conn_suss
This bit is used on ABR connections to suspend transmission. It should be initialized to
‘
0
’
.
drop
These two bits are used to indicate which physical drop will be used for this connection. Traffic can
be scheduled on up to four drops.
buffer_offset
This field contains the offset into the buffer that the transmit data starts.
xmt_cmp_evt_mod
This two-bit field can optionally (based on a bit in the SEGBF control register) be logically ORed with
bits 8-7 of a transmit complete buffer event when it is generated by the segmentation logic. This field
will only be ORed when buffer address events are being generated. It will have no affect when LCD
addresses are being enqueued when a transmit complete event occurs.
seg_prc_Entry_point #
This four-bit field is loaded into the instruction pointer for both the LCD update processor and the cell
generation processor when a cell opportunity occurs for the LCD. The value loaded into this field
defines what type of cell will be generated by the segmentation logic. Possible types include raw 48-
and 52-byte cells, AAL5 cells, switch bound cells (48-byte payload), extended switch bound cells
(54-byte payload), and frame-based cells. The actual values that are associated with each type of
cell will be defined at a later time.
ATM_header #
This field contains the first four bytes of the ATM header.
segmentation_pointer
This field contains a pointer to the next data to be transmitted. In normal operation, this field is initial-
ized by the cell scheduler when a new frame is queued for segmentation.
current_CRC
This field contains the CRC as it is being built.
Current_Blocking_Count
This eight-bit field contains the current count of four-byte values that have been assembled into cells
and sent out on this LCD for all fix block or MPEG AAL types. Other than initialization, this field
should only be accessed by the hardware.
Fixed_Blocking_size #
This eight-bit field should be initialized by the software to contain the number of four-byte values that
constitute a packet. For MPEG2, this register should be set to x
’
2F
’
(4
x
’
2F
’
= 188 byte transport
stream packet).
Current_transport_stream_packetmented. Other than initialization, this field should only be accessed by the hardware.
Packets_per_AAL5_frame #
This eight-bit field should be initialized by the software to indicate how many packets should be con-
catenated into an AAL5 frame.
explicit_rate
This 16-bit field contains the explicit cell rate as defined for ABR traffic on this LCD.
current_rate
This 16-bit field contains the current cell rate as defined for ABR traffic on this LCD.
minimum_rate
This 16-bit field contains the minimum cell rate as defined for ABR traffic on this LCD.
backward_ptr
When software needs to send a backward RM cell, this 32-bit field should be updated with the
address of a buffer that contains the desired backward RM cell. After the segmentation logic trans-
mits the cell, this field is cleared by the hardware.
xmit_stat1
This 32-bit field contains a count of one of three things: the total number of user cells that have been
sent on this LCD, the total number of bytes that have been sent on this LCD, or the total number of
frames that have been sent on this LCD. This field should zeroed when the connection is initialized.
An event will be generated when this count wraps.
xmit_stat2
This 32-bit field contains a count of one of three things: the total number of user cells that have been
sent on this LCD, the total number of bytes that have been sent on this LCD, or the total number of
frames that have been sent on this LCD. This field should be zeroed when the connection is initial-
ized. An event will be generated when this count wraps.
threshold_1&2
These fields are compared to the upper 24 bits of the bytes_queued field to determine when a
threshold is crossed and the POOL ID for the received LCD should be changed.
ABR Code Variables Definitions
(Page 3 of 4)
Field Name
Field Description