Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP Posting-Version: version B 2.10.1 6/24/83; site aesat.UUCP Path: utzoo!aesat!bmw From: bmw@aesat.UUCP (Bruce Walker) Newsgroups: net.micro Subject: Re: hardware question (schematic) Message-ID: <207@aesat.UUCP> Date: Thu, 23-Aug-84 09:16:07 EDT Article-I.D.: aesat.207 Posted: Thu Aug 23 09:16:07 1984 Date-Received: Thu, 23-Aug-84 13:10:23 EDT References: <502@bunker.UUCP> Organization: AES Data Inc., Mississauga Ont., Canada Lines: 67 <> > I have an old TI thermal printer (PC100A) that works with their > 58/59 calculators. I thought it might be kind of neat to interface > it to my computer. > > problem : The five unidirectional logic lines in the interface > use a 0 volt to -10 volt logic. > > question: Is this TI logic some sort of standard? > Is there an easy way to interface it to TTL ? > > Someone suggested a high speed op amp, but isn't this overkill? > (the clock frequency is about 227khz ). > > Jeff Hagen > ittvax!bunker!jrh This logic is a P-channel MOS standard from old calculator days. The trouble with using your usual opamp in this application is the low slew rate. Using a high-speed opamp to correct this would be overkill. Here's a fairly simple (and cheap!!) circuit which could work for your thermal printer interface: TTL input ---> | | +12 V +-+-+ ^ | | | ========= 14 | RS232 | 1/4 |--------+ line driver | of a | (Gnd: pin 7) | 1488 |--------+ \_____/ 1 | O | | V | -12 V | | 1K 5% 1/4W +-----/\/\/\/----+--------> Output: 0 to -10 V | | 1N914 or ----- \ 1N4148 \ / / general purpose \ / 10K 5% \ silicon ===== / switching diode | \ | | | V | -12 V | === (common system ground) /// One channel is shown. There are 4 drivers in one 1488 package, so you'll need two packages. Any old 1488 will do: TI (75188), Fairchild, Motorola etc. The buffer IC was chosen because of its popularity, there are interface IC's specifically for this kind of job but they are more expensive and/or scarce. The circuit was taken from the "Applications" section of the MC1488 data sheet in the Motorola 1983 "Linear & Interface IC's" data book. Bruce Walker {allegra,ihnp4,linus,decvax}!utzoo!aesat!bmw