Talk:MIL-STD-1553

From Wikipedia, the free encyclopedia

Thanks for adding the links --redstucco 09:29, 1 December 2005 (UTC)

There has been some discussion as to WHAT European (Western), Russian and Chinese avionics buses look like. I was told informally that the Russians cloned the 1553. Information on Russian and Chinese stuff is scant! It would be good if readers could contribute to this area and provide a link to it.

[edit] Inconsistency

The last paragraph seems to imply that the bus is only (or primarily) used for fly-by-wire systems, but the rest of the article does not discuss this, and maybe contradicts it. What is right?

[edit] Bus controller paragraph is jumbled up

Could the author take a look and fix it up?

"Messages consists of one or more 16-bit words (command, data or status)...."

I believe this section needs to have some ambiguity removed.

The "message" consists of 20 bit times: three bit/clock times for sychronization and to indicate of the type of word contained in the data bit times (command, data, or status), followed by sixteen bit/clock times for a 16 bit word, and finally a parity bit.

The first three bit times are the only ones allowed to hold a constant voltage level for one and one half bit times. The voltage transition in the middle of the first three bit times (1½ clock clycles)starts the timing for self synchonization of the data bits at the receiving end. The direction of transition (low to high) or (high to low) indicates the type of word to follow (command, data, or status).

The remaining 17 bits are required to make a voltage transition within one bit/clock time. If there is a change in a data bit from one to zero (10) or vice versa (01), the transition between polarities happens in the middle of the bit time. If a one is followed by a one (11), or if a zero is followed by a zero (00), the transition happens at the biggining of the bit time.

The direction of the voltage transition (high to low or low to high) durring the last 17 bit times is a function of the current bit value and the preceeding bit. The initial voltage transition direction is a function of the last transition of the sychronization signal and the value of the first bit.

If the transmitted data stays all zeros (0000000000000000) or all ones (1111111111111111), the resulting signal durring the 16 bit/clock times will be a square wave that is the same frequency as the clock (a full cycle in each bit time). A data pattern of alternating ones and zeros (1010101010101010) or (0101010101010101) will produce a square wave one half the clock frequency.

The parity bit follows the same rules as the data bits.

This can be better understood by a carefull reading of MIL-STD-1553B or by seeing the diagram under Manchester line code[[1]] here[[http://upload.wikimedia.org/wikipedia/commons/thumb/9/90/Manchester_encoding_both_conventions.svg/650px-Manchester_encoding_both_conventions.svg.png. ]]

207.5.226.145 01:59, 6 January 2007 (UTC) 207.5.226.145 02:13, 6 January 2007 (UTC) 207.5.226.145 00:37, 9 January 2007 (UTC)