PEB 2091
PEF 2091
Operational Description
4.7.2.1 Complete Loop-Back
When receiving the EOC-command LBBD in Auto mode, the NT IEC-Q does not close
the loop-back immediately. Because the intention of this loop-back is to test the complete
NT, the IEC-Q passes the complete loop-back request on to the next downstream
device. This is achieved by issuing the C/I-code AIL in the "Transparent" state or C/I =
ARL in states different than "Transparent" (see "State Machine in NT Modes", page 160).
If the downstream device is not able to close the complete loop-back, a MON-8-message
LBBD may be returned to the NT IEC-Q. This then will close the complete loop-back
within the IEC-Q itself (B1 + B2 + D-channels). All remaining IOM®-2-information
(monitor, C/I-channel as well as the bits MR and MX) are still read from the IOM®-2 or
the µP interface (if used). For this reason it is still possible for a layer-2 device to
deactivate the NT despite the fact that the loop-backs are controlled by the exchange.
Note 53: If operated in EOC Auto mode, the complete loop-back can only be
closed in the IEC-Q if previously the EOC-command LBBD was
received. Without this EOC-message the MON-8-command LBBD will be
ignored.
If operated in EOC Transparent mode, a complete loop-back may be
closed at any time with MON-8 LBBD.
In EOC Auto mode the complete loop-back is reset after RTN has been received in the
EOC-channel. In the EOC Transparent mode MON-8 NORM is used for this purpose. No
reset as for loop-backs #1 or #3 is required for loop-back #2. The line is active and ready
for data transmission.
As an example Figure 81 illustrates these two options if the IEC-Q is used together with
the SBC-X and the ICC.
C/I = AIL/ARL
U
SBCX
2B + D
IEC-Q
2B + D
EOC = "LBBD"
Auto-Mode
MON-8 "LBBD"
ICC
ITD04219
Figure 81
Complete Loop-Back Options in NT modes
Semiconductor Group
189
Data Sheet 01.99
INFINEON [ Infineon ]
