cx28250 Mindspeed Technologies, cx28250 Datasheet - Page 60

• Manufacturer Part Number: cx28250
• Description: Cx28250 Atm Physical Interface Phy Devices
• Manufacturer: Mindspeed Technologies

2.0 Functional Description
2.3 SONET/SDH Framer and Overhead Processor
Figure 2-10. J0/J1 Buffer Behavior
2-24
0x6B, octet 0
.
.
.
octet 54
octet 55
octet 56
octet 57
octet 58
octet 59
octet 60
octet 61
octet 62
octet 63
octet 1
octet 2
octet 3
octet 4
String to be transmitted: 00 01 02 03 04 05 06 07 08 09 0A ... 3B 3C 3D 3E 3F
.
.
.
2.3.4.1 J1
State of the J1 buffer
after the 1st frame
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The Path Trace byte, J1, is a circular 64-byte buffer that carries the Path Trace
message, so a receiving Path Terminating Equipment (PTE) can verify continued
connection to the transmitting PTE. This buffer overwrites when full. This
message is user programmable but generally is an 8-bit ASCII CLLI™ code
padded with ASCII NULL characters and terminated with CR and LF characters
making up 64 bytes total. If Path Trace is enabled, the user is required to enter a
message or the current contents of the transmit buffer will be transmitted. If J1 is
disabled, then 64 zeros are transmitted. J1 can be disabled via register TXPTH
(0x0E), bit 7. The J1 transmit buffer is located in register TXPTHBUF (0x69).
The J1 receive buffer is RXPTHBUF (0x6B). If the incoming message differs
from the data stored in the receive buffer from the previous message received, an
interrupt appears in register PTHINT (0x3F) bit 1.
reception.
Figure 2-10
Mindspeed Technologies
State of the J1 buffer
after the 2nd frame
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illustrates how the J1 buffer behaves during transmission and
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06
State of the J1 buffer
after the 3rd frame
Transmitter was at this point in the string when
the receiver obtained frame alignment.
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™
05
06
07
ATM Physical Interface (PHY) Devices
State of the J1 buffer
after the 64th frame
28250-DSH-002-C
3C
3D
05
06
07
08
09
3B
3E
3F
00
01
02
03
04
CX28250
100992_012a