rzh@lll-lcc.UUCP (Roger Hanscom) (04/12/89)
Does Anybody have a reference to complete schematics for a
video interface that uses the 6845 or similar chip?? Is there
an "application note" on the 6845 that shows some video
circuits?? I'd like to build a Hercules clone type circuit,
but not on the PC bus -- perhaps as a serial device?? I think
that I saw plans for a custom card (for the Apple??) that uses
the 7220?? chip in R-E a while back. Are there others??
roger rzh%freedom.llnl.gov@lll-lcc.llnl.gov
ucbvax!lll-lcc!freedom!rzh
Upstairs, Over a Vacant Lot, Inc.
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==================================================================wte@ncrcae.Columbia.NCR.COM (Bill Eason) (04/13/89)
In article <2414@lll-lcc.UUCP> rzh@lll-lcc.UUCP (Roger Hanscom) writes: >Does Anybody have a reference to complete schematics for a >video interface that uses the 6845 or similar chip?? Is there >an "application note" on the 6845 that shows some video >circuits?? It seems that my first microprocessor textbook had the complete schematics and programs for a 6800-based terminal, including a 6845-based video interface. I've never built it, but I do remember looking through the chapters on 68xx peripheral chips, and most had fairly complete discussions on how to use them: the 6821 PIA (Peripheral Interface A(dapter?)), the 6845 (I think), and others. The book is at home, but its title was something like __Using Microprocessors and Microcontrollers: the Motorola 6800__, or something like that. If the book is of interest to anyone, I can check on it when I get home. Hope this helps, -Bill -- Bill Eason (803) 791-6419 ...!ucbvax!sdcsvax!ncr-sd!ncrcae!sauron!wte NCR Corporation ....!rutgers!mcnc!ece-csc!ncrcae!sauron!wte E & M Columbia 3325 Platt Springs Rd. West Columbia, SC 29169
myers@hpfcdj.HP.COM (Bob Myers) (04/15/89)
>Does Anybody have a reference to complete schematics for a >video interface that uses the 6845 or similar chip?? Is there >an "application note" on the 6845 that shows some video >circuits?? I'd like to build a Hercules clone type circuit, >but not on the PC bus -- perhaps as a serial device?? I think >that I saw plans for a custom card (for the Apple??) that uses >the 7220?? chip in R-E a while back. Are there others?? The 6845 is pretty up in years now, but information - including an application note - should still be available from your friendly neighborhood Motorola rep/distributor. You might also try Hitachi - they are/were a second source for the 6845. The 6845 is, by current standards, a pretty "dumb" video controller. It is intended to provide memory control and sync signals for a "character generator" type of video display - i.e., one where you toss ASCII into a small RAM, and the characters are generated by running this code through a character ROM. The chip can be used, though, to control a simple dumb frame buffer for a graphics or bit-mapped alpha display. The 7220 is a step up; it was introduced by NEC around, oh, 1983 or so (as my fuzzy memory recalls), and includes some ability to manipulate the frame buffer data (drawing lines, circles, etc.) in addition to providing the video timing. It's probably mor widely available at this time, and will give you considerably better functionality. If you'd really like to get closer to the "state-of-the-art", get in touch with your local Texas Instruments rep/dealer/whatever and look into the 34010 and related chips (such as the 34070 color map). Many current and reasonably slick display cards for the PC market are based on this chip. Be prepared to spend a good deal more for it, though, as compared with the "dumb" controllers such as the 6845. Bob Myers KC0EW HP Graphics Tech. Div.| Opinions expressed here are not Ft. Collins, Colorado | those of my employer or any other {the known universe}!hplabs!hpfcla!myers | sentient life-form on this planet.
myers@hpfcdj.HP.COM (Bob Myers) (04/15/89)
/ hpfcdj:sci.electronics / myers@hpfcdj.HP.COM (Bob Myers) / 12:54 pm Apr 14, 1989 / >Does Anybody have a reference to complete schematics for a >video interface that uses the 6845 or similar chip?? Is there >an "application note" on the 6845 that shows some video >circuits?? I'd like to build a Hercules clone type circuit, >but not on the PC bus -- perhaps as a serial device?? I think >that I saw plans for a custom card (for the Apple??) that uses >the 7220?? chip in R-E a while back. Are there others?? The 6845 is pretty up in years now, but information - including an application note - should still be available from your friendly neighborhood Motorola rep/distributor. You might also try Hitachi - they are/were a second source for the 6845. As far a complete schematics, check out the "TV Typewriter Cookbook" (I think that was the title - it's close, anyway) by Don Lancaster. As I recall, Don's designs were based on the 6845. A good intro to basic video display drivers, in any event. The 6845 is, by current standards, a pretty "dumb" video controller. It is intended to provide memory control and sync signals for a "character generator" type of video display - i.e., one where you toss ASCII into a small RAM, and the characters are generated by running this code through a character ROM. The chip can be used, though, to control a simple dumb frame buffer for a graphics or bit-mapped alpha display. The 7220 is a step up; it was introduced by NEC around, oh, 1983 or so (as my fuzzy memory recalls), and includes some ability to manipulate the frame buffer data (drawing lines, circles, etc.) in addition to providing the video timing. It's probably mor widely available at this time, and will give you considerably better functionality. If you'd really like to get closer to the "state-of-the-art", get in touch with your local Texas Instruments rep/dealer/whatever and look into the 34010 and related chips (such as the 34070 color map). Many current and reasonably slick display cards for the PC market are based on this chip. Be prepared to spend a good deal more for it, though, as compared with the "dumb" controllers such as the 6845. Bob Myers KC0EW HP Graphics Tech. Div.| Opinions expressed here are not Ft. Collins, Colorado | those of my employer or any other {the known universe}!hplabs!hpfcla!myers | sentient life-form on this planet. ----------
jimc@iscuva.ISCS.COM (Jim Cathey) (04/28/89)
In article <16750021@hpfcdj.HP.COM> myers@hpfcdj.HP.COM (Bob Myers) writes: >The 6845 is pretty up in years ... >The 6845 is, by current standards, a pretty "dumb" video controller... >The 7220 is a step up; it was introduced by NEC around, oh, 1983 or so (as my >fuzzy memory recalls), and includes some ability to manipulate the frame >buffer data (drawing lines, circles, etc.) in addition to providing the video >timing. It's probably mor widely available at this time, and will give you >considerably better functionality. The 6845 is definitely dated, but it's widely available and quite cheap ($2 in quantity). If all you use it for is a timing controller it's quite fine. We use it in our bit-mapped graphics systems, and it works just ducky. The 7220 is more functional on a checkoff list, but it's also extremely slow. Our design (using a 7 MHz 68000 to do drawing) kicks the cookies out of a 7220. (An 8 MHz 68000 is $6 in quantity). To get speed out of a 7220 you can't use its built-in drawing stuff, so you might as well just use the cheaper timing controller. The TI 34010 _is_ a much better way to go, but it's about $70 each. And you still need a bunch more stuff (memory, palette, interfacing, glue...) Not for the faint of heart. +----------------+ ! II CCCCCC ! Jim Cathey ! II SSSSCC ! ISC Systems Corp. ! II CC ! TAF-C8; Spokane, WA 99220 ! IISSSS CC ! UUCP: uunet!iscuva!jimc ! II CCCCCC ! (509) 927-5757 +----------------+ "With excitement like this, who is needing enemas?"