xrt94l33 Exar Corporation, xrt94l33 Datasheet - Page 189

• Manufacturer Part Number: xrt94l33
• Description: Multi-channel, Multi-function Device Aggregates 3 Ds3/e3/sts-1 Into Oc3/stm-1
• Manufacturer: Exar Corporation

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3-CHANNEL DS3/E3/STS-1 TO STS-3/STM-1 MAPPER IC DATA SHEET
STEP 1b – Write a “1” into Bit 2 (Insertion Memory RESET*), within the “Transmit ATM Cell – Memory
Control” Register; as depicted below.
Transmit ATM Cell – Memory Control Register (Address = 0xNF13)
Note:
STEP 2 – Check and Verify that there is sufficient space available (within the Transmit Cell Insertion
Buffer) to handle this cell.
This can be accomplished by one of two approaches.
• Polling approach
• Interrupt-driven approach.
Each of these approaches is described below.
Executing STEP 2 using the Polling Approach
The user can determine whether or not there is room (to write another ATM cell of data) in to the “Transmit
Cell Insertion” Buffer” by polling the state of Bit 1 (Insertion Memory ROOM) within the “Transmit ATM Cell –
Memory Control Register” as depicted below.
Transmit ATM Cell – Memory Control Register (Address = 0xNF13)
If Bit 1 (Insertion Memory ROOM) is set to “1” then the “Transmit Cell Insertion Buffer” is NOT too full to
accept another cell. At this point, the Microprocessor can now move onto STEP 3.
Conversely, if Bit 1 is set to “0” then the “Transmit Cell Insertion Buffer” is too full to accept another cell. The
Microprocessor Interface should continue to poll the state of this bit-field and wait until this bit-field toggles to
“1”.
Executing STEP 2 using the Interrupt-Driven Approach
In order to reduce or eliminate the Microprocessor Overhead of continuously polling the state of Bit 1, the user
can use the “Transmit Cell Insertion” Interrupt feature, within the chip. If the Microprocessor invokes this
feature, then the XRT94L33 will generate an interrupt anytime a cell (residing in the Transmit Cell Insertion
Buffer) has been inserted into the “Transmit Output Data Path” (thereby freeing up some space within the
Transmit Cell Insertion Buffer).
B
B
R/O
R/O
IT
IT
0
0
7
7
This step should typically be performed upon power-up, prior to writing in any ATM cell data into the “Transmit
Cell Insertion Buffer”. This step is not necessary after the first cell has been written into the “Transmit Cell
Insertion Buffer” following a power cycle to the chip.
Unused
Unused
B
B
R/O
R/O
IT
IT
0
0
6
6
B
B
R/O
R/O
IT
IT
0
0
5
5
Extraction
Extraction
RESET*
RESET*
Memory
Memory
B
B
R/W
R/W
IT
IT
1
1
4
4
189
Extraction
Extraction
Memory
Memory
CLAV
CLAV
B
B
R/W
R/W
IT
IT
0
0
3
3
Insertion
Insertion
RESET*
RESET*
Memory
Memory
B
B
0->1
R/W
R/W
IT
IT
1
2
2
Insertion
Insertion
Memory
Memory
ROOM
ROOM
B
B
R/W
R/W
IT
IT
X
1
1
1
XRT94L33
Write SoC
Write SoC
Insertion
Insertion
Memory
Memory
Rev.1.2.0.
B
B
R/W
R/W
IT
IT
0
0
0
0