Thanks Peter, useful and detailed information. I'd been playing around with homebuilt 8-bit micro projects (which usually resembled a cluster of ICs buried under heaps of spaghetti-wiring on stripboard :o) which amazingly, usually worked, but never managed to connect a PC keyboard to one of them. Sounds a bit more complicated than I thought it might've been, with those timing issues!
Ian. > -----Original Message----- > From: pgraf > Sent: 17 November 2001 15:38 > To: ql-users > Cc: pgraf > Subject: [ql-users] Q40/Q60 keyboard interface > > > Hi Ian, > > >Similar information about the Q40 keyboard port would be useful too. > > The input is a 6 pin DIN connector. Almost every keyboard has > a leaflet to > describe the pinout, so I don't repeat it here. > > The Q40/Q60 keyboard transmission protocol is clocked serial (with the > keyboard as clock source), 11 bits in length. One start bit > (logic 0), 8 > data bits (LSB first), one odd parity bit and a stop bit > (logic 1). The > clock rate is about 10-20 KHz and can vary from keyboard to > keyboard. The > keyboard data format is similar to 8-odd-1 asynchronous transmission > format. However, the bit rate > from keyboard to keyboard can vary significantly so it is > necessary to use > a clocked serial interface with a receive clock input. The Q40/Q60 LSI > logic reads the data bits on the falling "edge" of each clock > pulse. The > exact timing and analogue rise/fall behaviour is very tricky > and not well > defined. I had to use things like digital oversampling to > support a wide > range of keyboards. Both CLOCK and DATA lines are implemented on the > keyboard end as open-collector outputs with pull-up resistors to +5V. > > The PC keyboard interface is fairly nasty to implement. The > problem with > the PC keyboard is that it uses the PC's on-board Intel 8741 (or > equivalent) single-chip microprocessor and the only way to exactly > reproduce its behaviour is to use the same chip. AFAIK the > 8741 is still > implemented as part of new PCs, within the PC chipset. Of > course, I wanted > no Intel chips on the Q40 ;-) > > Hope this was useful for you. > > Peter > > > Visit our website at http://www.ubswarburg.com This message contains confidential information and is intended only for the individual named. If you are not the named addressee you should not disseminate, distribute or copy this e-mail. Please notify the sender immediately by e-mail if you have received this e-mail by mistake and delete this e-mail from your system. E-mail transmission cannot be guaranteed to be secure or error-free as information could be intercepted, corrupted, lost, destroyed, arrive late or incomplete, or contain viruses. The sender therefore does not accept liability for any errors or omissions in the contents of this message which arise as a result of e-mail transmission. If verification is required please request a hard-copy version. This message is provided for informational purposes and should not be construed as a solicitation or offer to buy or sell any securities or related financial instruments.
