Aviation Electronics Technician 1 - Historic Naval Ships Association

BINARY-CODED WORD INTERFACE.— Thecontrol signals in the ICCG interface are primarily in abinary-coded word format. The binary words are shiftedinto and out of the crew ICS panels, the IRC panel, andthe SLU on pairs of multiplex lines. The crew ICS panelsand the IRC have unique binary word addresses that areidentified by a roll call sequence performed in the SLU.Every 25 milliseconds, each crew panel and the IRC areinterrogated for a change-of-status by the SLU. Thischange-of-status data is stored in the SLU until it istransferred to the general-purpose digital computer(GPDC) for permanent storage. The GPDC will bediscussed in a later chapter of this TRAMAN. Thechange-of-status data is then processed by the SLU toproduce mode forcing signals that are sent to theappropriate peripheral and ICCG components.HARD-WIRE SIGNAL INTERFACE.— Thevolume control signals and backup mode control andstatus signals are interfaced by separate lines betweenthe components. These signals are analog voltages andground circuits. These signals produce changes in thecomponents as the controls are adjusted or pressedwithout being processed first.ICCG IndicatorsMost of the indicators in the ICCG are either modeor function status indicators that come on amber andgreen. When the indicator comes on green, it means thatthe corresponding function is available for selection.When that function is selected, the indicator will turn toamber. With the indicator off, that function is notavailable for selection.On the IRC, the IFPM indicators will illuminatewhen a fault is detected in the correspondingcomponent. The S indicators on the crew panels willilluminate red when the secure mode of operation isselected for that particular radio system. The indicatorsin the frequency selection section of the IRC come onred when frequency selection is available.Encoded and Decoded Word FormatAll the components in the ICCG, except for the threeLS-602/AI panels, have identical binary encoding anddecoding circuits. The encoding circuits transform asignal function into a binary word in the Manchesterformat for transmission to another component. Thedecoding circuits transform the Manchester signalfunctions from another component into basic signalfunctions for application to processing and controlcircuits within that component.Each of the components in the ICCG, except theLS-602/AI, have a unique binary word address. Thecomponent responds to an interrogation by the SLU onlywhen its specific address is recognized. The addressesare incorporated into the 36-bit ICCG word format.Each bit is a status or control function, or a part of the5-bit component address that has a permanentlyassigned slot in the 36-bit format.The 36-bit words are serially generated and seriallytransmitted binary bit words. Each bit is either a 1 or a0. A logic 1 corresponds to a voltage level between 5.0and 8.5 volts dc. A logic 0 corresponds to a voltage levelbetween -0.5 and –1.5 volts dc.ENCODED WORD FORMAT.— Encoded wordformat is setup for 36-bits that are either status/controlfunction information or component addresses. Bit 1 isthe control bit and is always a 1.Bits 2 through 6 are the address bits. Each componenthas its own unique binary configuration. Oneexample of this is that the SLU recognizes the binarynumber 01010 as the pilot crew ICS panel. Should thisconfiguration show up in bits 2 through 6, then the SLUwill process on the command data from the pilot ICSpanel during the 36-bit word cycle. Each componentaddress word is designated by the decimal equivalent toits binary value. With the above example, the pilot ICSpanel 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 housekeeping.It is always 0 for encoded words.Bit 8 is the enter bit for binary housekeeping. In theencoded 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 thebinary circuitry. This system uses the odd parity check.If there are an even number of 1’s in the first 35 bits, bit36 will be a 1. If the total number of 1’s in the first 35bits is odd, bit 36 will be a 0. When a component receivesthe 36-bit encoded word, its decoder checks the parityby counting the 1’s. If it comes up with an even numberof 1’s, the word is not processed and a BITE indicatoris illuminated on the component that transmitted thefaulty data word.DECODED WORD FORMAT.— The decodedword format is similar to the encoded word format withjust a few differences. Bit 1, bits 9 through 34, bit 35 andbit 36 are the same as in the encoded word. Bits 21-5