BINARY-CODED WORD INTERFACE.— The control signals in the ICCG interface are primarily in a binary-coded word format. The binary words are shifted into and out of the crew ICS panels, the IRC panel, and the SLU on pairs of multiplex lines. The crew ICS panels and the IRC have unique binary word addresses that are identified by a roll call sequence performed in the SLU. Every 25 milliseconds, each crew panel and the IRC are interrogated for a change-of-status by the SLU. This change-of-status data is stored in the SLU until it is transferred to the general-purpose digital computer (GPDC) for permanent storage. The GPDC will be discussed in a later chapter of this TRAMAN. The change-of-status data is then processed by the SLU to produce mode forcing signals that are sent to the appropriate peripheral and ICCG components. HARD-WIRE SIGNAL INTERFACE.— The volume control signals and backup mode control and status signals are interfaced by separate lines between the components. These signals are analog voltages and ground circuits. These signals produce changes in the components as the controls are adjusted or pressed without being processed first. ICCG Indicators Most of the indicators in the ICCG are either mode or function status indicators that come on amber and green. When the indicator comes on green, it means that the corresponding function is available for selection. When that function is selected, the indicator will turn to amber. With the indicator off, that function is not available for selection. On the IRC, the IFPM indicators will illuminate when a fault is detected in the corresponding component. The S indicators on the crew panels will illuminate red when the secure mode of operation is selected for that particular radio system. The indicators in the frequency selection section of the IRC come on red when frequency selection is available. Encoded and Decoded Word Format All the components in the ICCG, except for the three LS-602/AI panels, have identical binary encoding and decoding circuits. The encoding circuits transform a signal function into a binary word in the Manchester format for transmission to another component. The decoding circuits transform the Manchester signal functions from another component into basic signal functions for application to processing and control circuits within that component. Each of the components in the ICCG, except the LS-602/AI, have a unique binary word address. The component responds to an interrogation by the SLU only when its specific address is recognized. The addresses are incorporated into the 36-bit ICCG word format. Each bit is a status or control function, or a part of the 5-bit component address that has a permanently assigned slot in the 36-bit format. The 36-bit words are serially generated and serially transmitted binary bit words. Each bit is either a 1 or a 0. A logic 1 corresponds to a voltage level between 5.0 and 8.5 volts dc. A logic 0 corresponds to a voltage level between -0.5 and –1.5 volts dc. ENCODED WORD FORMAT.— Encoded word format is setup for 36-bits that are either status/control function information or component addresses. Bit 1 is the control bit and is always a 1. Bits 2 through 6 are the address bits. Each com- ponent has its own unique binary configuration. One example of this is that the SLU recognizes the binary number 01010 as the pilot crew ICS panel. Should this configuration show up in bits 2 through 6, then the SLU will process on the command data from the pilot ICS panel during the 36-bit word cycle. Each component address word is designated by the decimal equivalent to its binary value. With the above example, the pilot ICS panel address 01010 is equal to decimal 10. Therefore, the pilot ICS panel designation is word 10. Bit 7 is the tag bit needed for binary word house- keeping. It is always 0 for encoded words. Bit 8 is the enter bit for binary housekeeping. In the encoded words it is always 1. Bits 9 through 34 are the command functions, status, or spare bits. Bit 35 is a command function, status, spare, or set-zero housekeeping bit. Bit 36 is the parity bit used for self-check in the binary circuitry. This system uses the odd parity check. If there are an even number of 1’s in the first 35 bits, bit 36 will be a 1. If the total number of 1’s in the first 35 bits is odd, bit 36 will be a 0. When a component receives the 36-bit encoded word, its decoder checks the parity by counting the 1’s. If it comes up with an even number of 1’s, the word is not processed and a BITE indicator is illuminated on the component that transmitted the faulty data word. DECODED WORD FORMAT.— The decoded word format is similar to the encoded word format with just a few differences. Bit 1, bits 9 through 34, bit 35 and bit 36 are the same as in the encoded word. Bits 2 1-5