DS21458-W+ Maxim Integrated, DS21458-W+ Datasheet - Page 68

• Manufacturer Part Number: DS21458-W+
• Description: Network Controller & Processor ICs
• Manufacturer: Maxim Integrated

Specifications of DS21458-W+

• Product: Framer
• Number Of Transceivers: 4
• Data Rate: 64 Kbps
• Supply Current (max): 328 mA
• Maximum Operating Temperature: + 70 C
• Mounting Style: SMD/SMT
• Package / Case: CSBGA
• Minimum Operating Temperature: 0 C
• Operating Supply Voltage: 3.3 V
• Supply Voltage - Max: 3.465 V
• Supply Voltage - Min: 3.135 V
• Part # Aliases: 90-21458+W00

11.2 Automatic Alarm Generation
The device can be programmed to automatically transmit AIS or remote alarm.
11.2.1 Auto AIS
When automatic AIS generation is enabled (E1TCR2.1 = 1), the device monitors the receive side framer
to determine if any of the following conditions are present: loss of receive frame synchronization, AIS
alarm (all ones) reception, or loss of receive carrier (or signal). If any one (or more) of the above
conditions is present, then the framer will either force an AIS or remote alarm.
11.2.2 Auto RAI
When automatic RAI generation is enabled (E1TCR2.0 = 1), the framer monitors the receive side to
determine if any of the following conditions are present: loss of receive frame synchronization, AIS alarm
(all ones) reception, or loss of receive carrier (or signal) or if CRC-4 multiframe synchronization cannot
be found within 128ms of FAS synchronization (if CRC-4 is enabled). If any one (or more) of the above
conditions is present, then the framer will transmit a RAI alarm. RAI generation conforms to ETS 300
011 specifications and a constant remote alarm will be transmitted if the DS21455/DS21458 cannot find
CRC-4 multiframe synchronization within 400ms as per G.706.
Note: It is an illegal state to have both automatic AIS generation and automatic remote alarm
generation enabled at the same time.
11.2.3 Auto E-Bit
When automatic E-Bit generation is enabled (E1TCR2.2 = 1), and the transmitter is in CRC-4 mode, the
transmitter will automatically set the E-Bit according to the following.
Table 11-2. Auto E-Bit Conditions
Receive CRC-4 disabled
Receive CRC-4 enabled but not synchronized
Receive CRC-4 enabled, Synchronized, with CRC Sub Multiframe codeword error
Receiver synchronized in CRC-4 mode with no CRC Sub Multiframe codeword errors
11.2.4 G.706 CRC-4 Interworking
G.706 Specifies a method to allow automatic interworking between equipment with and without CRC-4
capability. When basic frame alignment is established the device begins searching for the CRC-4
alignment pattern. If after 8ms the CRC-4 alignment is not found, it is assumed that frame alignment was
invalid and the device returns to the basic frame alignment search to establish new frame alignment.
After the new frame alignment is established the device starts a new 8ms search period for CRC-4
alignment. If CRC-4 alignment is found, the device starts CRC-4 performance monitoring and setting of
the transmitted E-bits according to G.706. (See the Auto E-bit section.) If CRC-4 alignment is not
achieved the device continues to return to the basic frame alignment procedure followed by an 8ms
search period for CRC-4. This process continues for 400ms. At the end of this 400ms period, it is
assumed that the far end equipment is non-CRC-4, the search for CRC-4 alignment is terminated and the
E-bits transmitter toward the far end equipment are set continuously = 0. The DS21455/DS21458 provide
a flexible method for implementing this procedure. Once the device is put into the receive CRC-4 mode, a
counter begins to run. The user can access this counter via Information Register 7.
CONDITION
68 of 269
DS21455/DS21458 Quad T1/E1/J1 Transceivers
STATE
E-BIT
0
0
0
1