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IBM2520L8767
IBM Processor for ATM Resources
Packet Header
Page 68 of 553
atmrm.chapt03.01
08/27/99
AAL5 Field Definitions
(Page 1 of 2)
Field Name
Field Description
Note
mode
This field selects the major mode for this LCD. The other fields are based on this value.
00 = Normal Mode
01 = Routed Mode
10 = Cut Thru Mode
11 = Scatter Mode
1
rtoTest
This is the reassembly timeout processing test-and-set bit. It is used by the IBM2520L8767, but
should be initialized to zero.
1
rtoEnable
If set, reassembly processing is enabled for this LC, if the LC is running AAL5 or is in FIFO mode.
1
tmpCLP
Used by the IBM2520L8767 to track the current state of the OR’d CLP bit for the current AAL5 packet.
This field should be set to zero at initialization. After initialization, the IBM2520L8767 maintains this
field.
1
tmpCongestion
Used by the IBM2520L8767 to track the current state of the OR’d congestion bit for the current AAL5
packet. This field should be set to zero at initialization time.
1
descState
This is used by the IBM2520L8767 for cut-through processing. This should be initialized to zero.
1
headerThresh
Specifies how much data should be received before poping a packet start event. If it is set to zero,
only complete packet events will be popped.
1
maxLength
Specifies the maximum amount of data that can be received per packet on this LC. If set to zero, the
value in RAALL Max SDU Length Register is used. This allows the maximum packet size to be set on
an LCD basis.
1
rxBuffAddr
This field is used by the IBM2520L8767, but should be initialized to zero by software. This field is used
to track the current packet under reassembly.
1
rxCcrc
This field is used by the IBM2520L8767 to maintain the CRC residue as the current packet is reas-
sembled. This field does not need to be initialized.
routedLcd
When routing cells, this field is used to fill in the LCD field of the packet header. This allows the user to
dynamically route cells back out the interface using a different LCD. The user should be sure to set the
free on transmit bit in this field as if it was in a packet header.
1
ctMode
Specifies cut-through Mode 6 when cleared and Mode 7 when set. Mode 6 DMAs the header when
the packet is complete, while Mode 7 DMAs the headers when the threshold is met.
1
cutThruThresh
Used to determine how much cut-through data is DMA’d.
1
dmaedHeader
This is used by the IBM2520L8767 for cut-through Mode 7 processing. This should be initialized to
zero.
1
numDesc
This is used by the IBM2520L8767 for scatter processing, and sould be initialized to zero.
1
numHeadBytes
Specifies how many bytes of data should kept with the packet header when DMAing the final DMA list
for a completed scatter packet. Must be less than the page size.
1
1. Software should set up this field.