From: Hársfalvi Levente (levente_at_terrasoft.hu)
Date: 2002-08-22 11:02:19
Hi!, Asbjørn Djupdal wrote: > But I can't see how to get rid of the 7406 chip. That's pretty simple. You can use the AVR portbits like they were open collector outputs: set the respective output bits (PORTD.0 and PORTD.1) to '0's, and activate them using the data direction register when it's neccessary (DDRD.0 and DDRD.1). With DDRD.0 =1, the pin is output (= a strong 0 level), with DDRD.0 = 0 the pin is input ( = the pin is left floating) and you can read its value from PIND.0 . That's probably all about it. There's a small chance that it won't be able to drive as many units on the IEC bus as the 7406 could (as the 7406 can sink more current). But from the safety's side, there shouldn't be any problems. The AVR portpins are well protected, the whole unit is pretty robust. Sometimes I've put AVRs with reverse alignment into the IC socket, and they all survived the accident without problems :-). If that, they should survive most accidents ;-). > Btw, this is my first hardware design. Cool :-). BTW, if it were smaller, it could call for a CompactFlash as media, rather than an old IDE HDD. If something at all, I especially like the noiseless operation of these old computers. Regards, L. Message was sent through the cbm-hackers mailing list
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