4 ms·
Okay, but to be fair I immediately recognised the "ready" signal 0xAA or 0x55 as "oh, it just toggles the bit every clock. That sounds oddly useful. You can pro
by boondaburrah 5y ago
Okay, but to be fair I immediately recognised the "ready" signal 0xAA or 0x55 as "oh, it just toggles the bit every clock. That sounds oddly useful. You can probably sync a clock or something on that." I've also run into situations where I'm counting bits and the flip-flop doesn't actually get set until the /next/ clock pulse, so having the phase change bit arrive one cycle early seems like a kludge around that sort of thing.
Ya gotta remember that Sony is hardware people so they do inscrutable things in software that probably turn out to make silicon implementation easier.
- ChuckMcM 5y agoFun, but somewhat obscure, fact is that Intel MDS systems (their "Big blue box" for developing software of their microprocessors) used 0x55 (ASCII 'U') to set the initial baud rate. When you turned them on they would read signal coming in on the console line, derive timing information from it and then set the baud rate and print out the greeting message.
- a2800276 5y agoUsing 0x55 to synchronize baud rate is fairly common. E.g. by coincidence just yesterday I was working with the ESP bootloader. The initialization sequence contains a SYNCH command with a bunch of 0x55s the processor uses to determine the baud rate. There should be a "Glossary of Common Byte Patterns" :)
- _Microft 5y agoI just remembered that I saw a list of magic numbers on rachelbythebay.com once and submitted it at https://news.ycombinator.com/item?id=30733067 https://news.ycombinator.com/item?id=30733067 Maybe you like that. 0x55 and 0xAA are also in there.
- wildzzz 5y agoSometimes called a barker code. You can have them start with large clock periods and then speed up so that the receiver is ready at the correct clock rate by the time the data is available in the transmission.
- jl6 5y agoPure coincidence that 0xAA55 marks the end of the PC master boot record?