
IBM2520L8767
IBM Processor for ATM Resources
atmrm.chapt05.01
08/27/99
ATM Transmit Buffer Segmentation (SEGBF)
Page 247 of 553
11.3: SEGBF Control Register
This register provides a mechanism to control the various programmable features of SEGBF. See
Note on
Set/Clear/Read Type Registers
on page 71 for more details on addressing.
‘U
Length
22 bits
Type
Clear/Set
Address
XXXX 1408 and 40C
Power On Value
X’00000’
Restrictions
None
P
P
P
P
L
L
H
P
I
C
F
F
N
M
R
L
P
O
P
I
5
E
21 20 19 18 17 16 15 14 13 12 11 10
9
8
7
6
5
4
3
2
1
0
Bit(s)
Description
21
When set, this bit will force all NUD cells with the PTI field of 111 to be excluded from the NUD cell counter.
20
When set, this bit will force all NUD cells with the PTI field of 110 to be excluded from the NUD cell counter.
19
When set, this bit will force all NUD cells with the PTI field of 101 to be excluded from the NUD cell counter.
18
When set, this bit will force all NUD cells with the PTI field of 100 to be excluded from the NUD cell counter.
17
When set, this bit will force all LCD address to be shifted by eight bytes when accessed by the segmentation logic. It is
meant to be used for diagnostic testing of the segmentation hardware.
16
When set, this bit will force all LCDs to be fetched from memory and not buffered in SEGBF.
15
When set, this bit will enable a function in the segmentation logic that replaces the HEC in the cell with a fourth byte of user
data from the LCD. The byte that replaces the HEC will be retrieved from a location in the LCD that is specified by the
Pre-pended header steering register.
14
This bit when set will enable the segmentation function which allows user data from the LCD to be pre-pended on the cells
as they are built. When enabled, the segmentation logic will always place three bytes of user-defined data from a location
in the LCD that is specified in the Pre-pended header steering register, into the cell buffer preceding the ATM header
before passing the cell to the next lower level.
13
This bit when set will cause the segmentation logic to pause when it reaches the idle state. Segmentation will not be con-
tinued until this bit has been reset. Care must be taken to leave this bit set for a very short duration so that segmentation
throughput will not be adversely affected.
12
When set, this bit will cause the segmentation logic to delay the cell immediately following the cell that contained the PCR
until the correct time. If reset, the last cell of the AAL5 frame that contained a PCR will be delayed.
11
When set, this bit will cause the segmentation logic to count the number of frames that have been sent instead of the num-
ber of cells that have been sent with CLP = 0. Both the register that counts these events across all LCDs as well as the VCI
specific field in a particular LCD are affected by this bit.