![](http://datasheet.mmic.net.cn/Exar-Corporation/XRT75R12DIB-L_datasheet_100141/XRT75R12DIB-L_106.png)
XRT75R12D
102
TWELVE CHANNEL E3/DS3/STS-1 LINE INTERFACE UNIT WITH SONET DESYNCHRONIZER
REV. 1.0.3
Figure 50 relates the contents within these 10 bits (within the H1 and H2 bytes) to the location of the J1 byte
(e.g., the very first byte of the STS-1 SPE) within the Envelope Capacity.
NOTES:
1.
If the content of the "Pointer Bits" is "0x00" then the J1 byte is located immediately after the H3 byte, within the
Envelope Capacity.
2.
If the contents of the 10-bit expression exceed the value of 0x30F (or 782, in decimal format) then it does not
contain a valid pointer value.
FIGURE 49. THE BIT-FORMAT OF THE 16-BIT WORD (CONSISTING OF THE H1 AND H2 BYTES) WITH THE 10 BITS,
REFLECTING THE LOCATION OF THE
J1 BYTE, DESIGNATED
FIGURE 50. THE RELATIONSHIP BETWEEN THE CONTENTS OF THE "POINTER BITS" (E.G., THE 10-BIT EXPRESSION
WITHIN THE
H1 AND H2 BYTES) AND THE LOCATION OF THE J1 BYTE WITHIN THE ENVELOPE CAPACITY OF AN STS-
1 FRAME
X
S
N
LSB
MSB
H2 Byte
H1 Byte
10 Bit Pointer Expression
521
520
* * * * * * * *
* *
436
435
E2
M0
S1
434
433
* * * * * * * *
* *
349
348
D12
D11
D10
347
346
* * * * * * * *
* *
262
261
D9
D8
D7
260
259
* * * * * * * *
* *
175
174
D6
D5
D4
173
172
* * * * * * * *
* *
88
87
K2
K1
B2
86
85
* * * * * * * *
* *
1
0
H3
H2
H1
782
781
* * * * * * * *
* *
697
696
D3
D2
D1
695
694
* * * * * * * *
* *
610
609
F1
E1
B1
608
607
* * * * * * * *
* *
523
522
C1/J0
A2
A1
TOH
The Pointer Value “0” is immediately
After the H3 byte