(b)  
Each navigation unit has three digital data input channels, each channel consisting of clock, data, and sync signals.

 D. INS - PMS Interface (On Airplanes with PMS).
 (1)  General
 (a)  
The INS operates in a PMS waypoint control mode or in an INS waypoint control mode.

 (b)  
The INS is placed in the PMS waypoint control mode, when the INS is turned on and two continuous valid control words are received from the PMS. If required, the INS can then be placed in the INS waypoint control mode, by commanding the mode at the PMS CDU. However, the INS can be returned to PMS waypoint control, by commanding the mode at the PMS CDU.

 (c)  
When the INS is in the PMS waypoint control mode, the INS responds to all data received from the PMS, and rejects all data inserted at the INS CDU. (INS CDU operates only as a display unit).

 (d)  
However, present position data is inserted only at the INS CDU, and may be loaded into the INS, in the PMS waypoint control mode or in the INS waypoint control mode.

 NOTE: A blank FROM/TO display on the INS CDU indicates PMS
____ waypoint control (waypoint data is entered at the PMS CDU).
 An illuminated FROM/TO display on the INS CDU indicates INS waypoint control.

 EFFECTIVITY

 AIRPLANES WITH DELCO INS  CONFIG 1  02 A Page 58  Apr 25/8734-41-00

Power Control and Distribution Circuits Block Diagram
Figure 19

EFFECTIVITY AIRPLANES WITH

CONFIG 1 DELCO INS
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 (e)  
The INS automatically reverts to the INS waypoint control mode and sets a malfunction code if: 1) A control word is not received from the PMS. 2) A control word is received from the PMS with a flight leg

 command but a FROM/TO is not received.

 (f)  
If the INS automatically reverts to INS waypoint control and the ground speed is greater than 75 knots, the INS cannot be returned to PMS waypoint control (PMS lockout); until the INS is down moded to STBY, or turned OFF and then turned on. If the ground speed is less than 75 knots the INS can be returned to PMS waypoint control without down moding the PMS.

 (g)  
If the transition to INS waypoint control is commanded and not automatic no malfunction codes are issued, the INS can therefore be commanded to return to PMS waypoint control regardless of ground speed and without down moding the INS.

 (h)  
When the INS is in the INS waypoint control mode the INS ignores all inputs from the PMS and responds to data inserted at the INS CDU (INS CDU is fully operational).

 (i)  
Any INS not receiving data directly from the PMS will operate totally independent of the PMS, except for position updates if triple mix is commanded.

 (2)  
PMS to INS Data.

 (a)  
The PMS transmits updated present position, FROM waypoints, TO waypoints and an INS control word to the INS. The PMS data to the INS is by a six wire clock-sync-data transmission. A PMS data warn discrete is also connected to the INS.

 (b)  
The INS transmits INS inertial present position to the PMS. The inertial present position is updated in the PMS by a DME-DME, or single DME solution, from PMS selected DME stations. This DME updated present position is then transmitted from the PMS to the INS. The transmitted PMS present position is used in the INS to update displayed present position.

 (c)  
In the PMS waypoint control mode the PMS transmits a waypoint flight plan (the FROM waypoint latitude and longitude, the TO waypoint latitude and longitude plus the latitudes and longitudes of the next seven waypoints). These waypoints are stored by the receiving INS.

 (d)  
The INS control word (from the PMS) contains a designation matrix to identify valid data, an odd parity bit and control bits. The control bits provide data for PMS operation of the INS, the data includes: Triple INS mixing, DME identification, INS waypoint control, waypoint alert, leg change command, INS action and malfunction code request, HSI test, and HSI warn.
　
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