Frank Eggink wrote:> Hello, > > is it possible to use io on a z80 to select different memory chips. > Something like bankswitching, using an out command to select a memory chip? > > Greetings > > FrankI designed a Z80 product for operation with 4Meg of Dram which used only a 74LS00 and 74LS04 for interfacing to the Drams. Without additional hardware support, it was possible to go to 64Meg, but I never tried it. This was in a commercial product called PBUFF, which was a centronics port driven printer buffer. The Z80 was getting a bit long in the tooth, and the need for large buffers, was overcome by manufacturers building more memory into their printers, so the product was dropped eventually. Sold 1000's of units world wide, well before the internet days. Also featured in Australian Electronics magazines, such as Silicon Chip. Around 1989 I think it was. schematics and source code at: http://www.dontronics.com/z80.html Please don't contact me for additional support. I am somewhere between old age and death these days, so I have trouble remembering it all, but you are very welcome to make use of the information on the pages and files. :-) Cheers Don... -- Don McKenzie Affiliate Program: http://www.dontronics.com/affiliate Site Map: http://www.dontronics.com/sitemap E-Mail Contact Page: http://www.dontronics.com/email No More Damn Spam: http://www.wizard-of-oz.com Parallax Propeller Powered .96" OLED module http://tinyurl.com/2vr2gr
z80 memory io selection
Started by ●February 7, 2008
Reply by ●February 7, 20082008-02-07
Reply by ●February 7, 20082008-02-07
"Frank Eggink" <freggink@gmx.net> wrote in message news:47aaff55$0$13746$ba620dc5@text.nova.planet.nl...> Hello, > > is it possible to use io on a z80 to select different memory chips. > Something like bankswitching, using an out command to select a memory > chip?Yus. You might want to look into the 64180, which is effectively the Z80 with bank switching ;). Tip: leave the vector area unbanked. Steve http://www.fivetrees.com
Reply by ●February 7, 20082008-02-07
John Speth wrote:> This will only work with SRAM because you will turn > off DRAM refreshing capability if you switch out DRAM.It is possible (albeit more complicated) to have the refresh logic handle multiple DRAM devices at once, regardless of which is currently selected. Bank-switching on old processors like the Z80 was more often used on ROMs than RAM... Regards, -- Mark McDougall, Engineer Virtual Logic Pty Ltd, <http://www.vl.com.au> 21-25 King St, Rockdale, 2216 Ph: +612-9599-3255 Fax: +612-9599-3266
