Honeywell ASPIRE-400 System Description, Installation And Maintenance Manual page 89

SYSTEM DESCRIPTION, INSTALLATION, AND MAINTENANCE MANUAL
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EFFECTIVITY
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ASPIRE-400
The SDU enters Standby state on start-up and stays in Standby state until
commanded to go into Active State via Label 272 from the TCP when the
following is true:
1 ORT configured for Aircraft Directed Dual Safety SATCOM.
When all the following are true:
1 ORT configured for Aircraft Directed Dual Safety SATCOM.
2 SSM of Label 272 is set to NO on the selected ARINC 429 MCDU
interface for at least 3 consecutives labels.
3 Bits 12-11 (Operational Mode Command) is 01b (SDU1 Active & SDU2
Standby) in Label 272 Operational Mode Command Word that is being
used.
The ACD sets the "ACDir Select Mode" to:
1 SDU1 Else
2 SDU2 (Operational Mode Command is set to 10b - SDU2 Active & SDU1
Standby).
NOTE: The priority is to use Label 272 from MCDU 1 when valid,
then MCDU 2 when Label 272 is missing/invalid from MCDU
1, then MCDU 3 when Label 272 is missing/invalid from both
MCDU 1 & 2.
The ACD keeps the "ACDir Select Mode" unaltered when all the following are
true:
1 SSM of Label 272 is set to FT.
2 Bits 12-11 (Operational Mode Command) is 01b (SDU1 Active & SDU2
Standby) or 10b (SDU2 Active & SDU1 Standby) in Label 272
Operational Mode Command Word that is being used.
NOTE: The priority is to use Label 272 from MCDU 1 when valid,
then MCDU 2 when Label 272 is missing/invalid from MCDU
1, then MCDU 3 when Label 272 is missing/invalid from both
MCDU 1 & 2.
The SDU transitions to Active State, else Standby State, when all the following
are true:
1 ORT configured for Aircraft Directed Dual Safety SATCOM.
2 The SDU number (per the strapping) is the same as "ACDir Select
Mode".
3 The DSD is not asserted.
Bits 11, 12 and 13 of CFDS Label 362 OCA Fault Summary Word are all set to
unavailable (1) when all the following are true:
1 ORT configured for Aircraft Directed Dual Safety SATCOM.
2 The SDU is in Active mode.
That SDU transitions to Standby state when the ORT configured for Aircraft
Directed Dual Safety SATCOM.
On entering Active mode, the ACD:
23-15-49
3rd rvw Draft as of:
29 January, 2020
Page 2-25
22 Apr 2019