User's Manual

ROCKWELL COLLINS
COMPONENT MAINTENANCE MANUAL with IPL
TDR-94, PART NO 622-9352
7
Downlink Request (DR) Field
The 5 bit DR field is used to request extraction of downlink messages from the
transponder by the interrogator. The codes are defined as follows:
D
R DE SCRIPTION
0 No downlink request
1 Request to send Comm B message
2 TCAS information available
3 TCAS infor mation available and request to send Comm B message
4 Comm B broadcast #1 available
5 Comm B broadcast #2 available
6 TCAS information and Comm B broadcast #1 available
7 TCAS information and Comm B broadcast #2 available
8 - 15 (Not assigned)
16 - 31 Com m D, not implemented in TDR-94/94D Class 3A
Mode S Transponders
8
Flight Status (FS) Field
The 3 bit FS field reports the flight status of the
airplane. The codes are defined as follows:
F
S ALERT SPI AIRBORNE/ON THE GROUND
0 no no airbor ne
1 no no on the ground
2 yes no airborne
3 yes no on the ground
4 yes yes either
5 no yes either
6 - 7 (Not assigned)
9
Identification ( ID) Field
The 13 bit ID field contains the 4096 identification code as selected
by the operator.
1
0 ELM Control (KE) Field
The 1 bit KE field defines the content of the ND and MD fields in Comm D
replies, i.e. DF number 24. This function is not implemented in the
TDR-94/94D Class 3A Mode S Transponders.
1
1 Message Comm B (MB) Field
The 56 bit MB field contains messages transmitted to the interrogator. In those
for m ats that use the ground initiated Comm B protocol, the MB field contains
an 8 bit subfield (BDS ) defining the contents of the Com m B message. BDS is
expressed in two 4-bit groups identified as BDS1 and BDS2.
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May 18/06