User's Manual

SYSTEM DESCRIPTION, INSTALLATION, AND MAINTENANCE MANUAL
eNfusion® HSD-440 Mark 2 Terminal
23-15-30 F-1
3 JUN 10
APPENDIX F: CMU MESSAGES
The CMU communicates with the HSD-440 Mark 2 Terminal using two types of communications:
Broadcast messages and Bit Oriented Protocol (BOP) messages. Both types of communication are
supported at the same time.
This section includes descriptions of the messages that the CMU will transmit to the HSD-440 Mark
2 Terminal and receive from the HSD-440 Mark 2 Terminal.
In this communication type, the CMU uses an ARINC 429 bus to convey status word exchanges,
join/leave words, and other control and command communications to the HSD-440 Mark 2 Terminal
using conventional ARINC 429 broadcast techniques.
The CMU can transmit messages to the HSD-440 Mark 2 Terminal and receive messages from the
HSD-440 Mark 2 Terminal using this communication type.
1. Understanding Messages Transmitted to the HSD-440 Mark 2 Terminal
This section provides details about the words sent to the HSD-440 Mark 2 Terminal from the CMUs:
• Understanding System Identification Label 172
• Understanding Status Word 1; Label 270
• Understanding Status Word 2; Label 276
• Understanding Protocol File Transfer to CMU via Williamsburg
A. Understanding System Identification Label 172
Each CMU transmits system identification label 172 (SAL 304) to the HSD-440 Mark 2
Terminal. Attachment 6 from ARINC Characteristic 758 describes the word format of this
label. Any other SAL is ignored.
B. Understanding Status Word 1; Label 270
Each CMU transmits status word 1 to the HSD-440 Mark 2 Terminal. The standby CMU
checks to see if its status words are the same as the active CMU using its cross-talk
connections.
The HSD-440 terminal uses bit 20 to determine which CMU is active. When bit 20 is set,
that CMU is active, and the other CMU should have its bit 20 cleared. In the event of an
error and both CMUs are shown as active, the CMU on input port 1 is considered active.
Table F-1 Status Word 1
Bit Label Meaning
9 270 Determines the position of the CMU in the cockpit; see Table F-2
10 270 Determines the position of the CMU in the cockpit; see Table F-2
20 270 Determines which CMU is active and which is on standby