Technical Provisions for Mode S Services and Extended Squitter

DRAFT - Working Paper ASP TSGWP11-01 for review by the TSG during the meeting in June 2011 in Paris
CD-6 Technical Provisions for Mode S Services and Extended Squitter
The setting of this bit is preferably dynamic. In case it is statically handled it should be forced to 1.
When this bit is dynamic, it is always equal to bit 7 of register 1716. It might be different from bit 25 of register 1816 since
the bits of registers 1816 to 1C16 are not reset once they are set. If the interface availability changes during the flight,
bit 33 of register 1016 and bit 7 of register 1716 will be updated accordingly whereas bit 25 of register 1816 will remain
unchanged.
This is explained in notes 1 and 2 of §A.2.2.1.
Note 1.— The intent of the capability bits in register number 1716 is to indicate that useful data are contained in the
corresponding transponder register. For this reason, each bit for a register is cleared if data becomes unavailable (see
§A.2.5.4.1) and set again when data insertion into the register resumes.
Note 2.— A bit set in register numbers 1816 to 1C16 indicates that the application using this register has been
installed on the aircraft. These bits are not cleared to reflect the real-time loss of an application, as is done for register
number 1716 (see §A.2.5.4.2).
It is also to be noted that register 1016 will be broadcast twice following the interface availability change. The first time
because bit 33 will change, then because bit 36 will also toggle approximately one minute later to indicate that the
content of register 1716 has changed.
CD.2.4.1.8 BIT 34 (SQUITTER CAPABILITY SUBFIELD)
This bit should be set as specified in Table A-2-16 of Appendix A.
The squitter capability subfield (SCS) is interpreted as follows:
0 = squitter registers are not updated
1 = squitter registers are being updated
SCS: This 1-bit squitter capability subfield reports the capability of the transponder to transmit extended squitter position
reports. It shall be set to 1 if BDS registers 05 and 06 {HEX} have been updated within the last ten plus or minus one
seconds. Otherwise, it shall be set to 0.
Bit 34 is therefore an AND of bits 1 and 2 of transponder register 1716 and the setting of this bit is dynamic.
Note that register 1016 will be broadcast twice in case bit 34 changes. The first time because bit 34 will change, then
because bit 36 will also toggle one minute later to indicate that the content of register 1716 has changed.
CD.2.4.1.9 BIT 35 (SI CODE CAPABILITY)
This bit should be set as specified in Table A-2-16 of Appendix A, item 6.
The surveillance identifier code (SIC) bit is interpreted as follows:
0 = no surveillance identifier code capability
1 = surveillance identifier code capability
Draft
SIC: This 1-bit surveillance identifier capability subfield reports the capability of the transponder to support the
surveillance identifier (SI) codes.
The setting of this bit is static. If the transponder software version handles SI codes then this bit should be set to 1.
CD.2.4.1.10 BIT 36 (COMMON USAGE GICB CAPABILITY REPORT)
This bit should be set as specified in Table A-2-16 of Appendix A, item 7.
Bit 36 toggles each time the common usage GlCB capability report (BDS code 1,7) changes. To avoid the generation of
DRAFT - Working Paper ASP TSGWP11-01 for review by the TSG during the meeting in June 2011 in Paris