> > Hallo Ethan, > > > Traditionally, RS232 was implemented on PETs with either an IEEE488 > > box (I have a couple) or a board that piggybacks into a ROM socket > > and taps R/W from somewhere (I have an ACIA board like that, too). > > I think I have this IEEE/RS232 interface on paper somewhere, (PET revealed > page 157) but if it is the right one??? I don't think so. Please tell us at > least of the used ICs. That could give us some more clues. I just got it off the shelf: it's a Microtech Portmaker. The memory map section of the manual (p13) looks like this: MEMORY MAP ---------- The ACIAs of the Portmaker board occupy the highest 16 locations of the ROM socket space where the board is inserted. For example: Commodore socket UD11: $A000 thru $AFFF ROM $A000 thru $AFF3 ACIA U8 (J1) $AFF0 thru $AFF3 ACIA U7 (J2) $AFF4 thru $AFFF The actual registers are ACIA U8 Control/Status $AFF0 ACIA U8 Data register $AFF1 ACIA U7 Control/Status $AFF4 ACIA U7 Data register $AFF5 ------------------------------------------------------------------------------ The Portmaker itself has an empty ROM socket for the displaced ROM, a 68B50, an empty socket for another 68B50, line drivers, and for select logic: 'LS21, 'LS393, 'LS30 and an 'LS139 _ ___ The three jumper leads go to R/W, IRQ, and Phi2 clock. As for those IEEE<->RS232 boxes I've got, they are TNW Corp (The Net Works) TNW-2000 boxes with no CPU, just an AY5-1013 UART, a bunch of TTL/CMOS logic ('LS00, 'LS32, 'LS27, 'LS02, 'LS08, 'LS279, 'LS10, 'LS04, 'LS85, 4049) and three 3440 IEEE drivers. The baud rate is controlled by a 555 timer with externally accessible potentiometer. There is also an 8-position DIP switch labelled: SW OPEN CLOSED FUNCTION 1 High Low Baud Rate 2 Even Odd Parity 3 Dis Enb Parity 4 PET Norm ASCII 5 8 0 IEEE 6 4 0 IEEE 7 2 0 IEEE 8 1 0 IEEE The power rating is unusual: 115/230V 50-400Hz 4W. I've never seen equipment rated to 400 Hz before. One has chips as new as 8310, the other 8009. The newer one has an AY-3-1015 UART, but is otherwise identical. I haven't had time to test either one out since I rescued them from the rubbish bin at Uni (the physics department used to use PETs). If I were making one from scratch, I'd probably wire a 6551 onto an adapter board and stick it in a ROM socket with little or no decoding. Only when I was using my PET every day did I worry about how much ROM space I had (MicroMON, BASIC AID and the ROM PET Rabbit). I only ever used 8K out of 12K. Even a dual 6551 board isn't too difficult to wire up, if you clobber the whole 4K socket. Speaking of ROMs, BG Micro (www.bgmicro.com) has 2532 ROMs for under $2. I just bought a stack to last me probably forever. They also sell cheap LCD panels that a PET could drive off the User Port - 4 bits for data and three control lines. They'd make great debugging tools. I have a dream for my Portmaker: in my copious free time, port the C64 PPP stack to the PET and hook my PET up to the Internet. If only someone made an Ethernet card that was easy to hook up to a 6502... -ethan
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