Henk in NL...Re: CF cards on classic machines (was Re: Another disk imaging project)

Ethan, the access that you describe is exactly what I do in my homebrew pdp8/e with the Core & I/O Board! I started out with a real IDE disk but bought an IDE-CF adapter, and it worked right away. BTW, in the source code is a description of the way I connected the IDE/CF card to the I/O Board. I started with an 8-bit datapath, that is fine for sending the commands, but reading the data is of course also 8 bits. In the beginning I did not consider that to be a real loss, but it annoyed me that I could not read properly the IDENT data result (manufacturer, type, size, etc.). So I "upgraded" the data path to 16 bit. But 8 bits works for sure! See www.pdp-11.nl/homebrew/pdp8/pdp8startpage.html (a page that is almost weekly updated!) - Henk, PA8PDP. On 8/5/05, Jim Brain <brain at jbrain.com> wrote: This is not an ATA feature I'm talking about, it's a CF feature... you can switch the Compact Flash card to use only 8-bit transfers, in case you need to connect the Compact Flash card to an 8-bit bus. Accessing a drive takes the following steps: 1. The address is asserted on lines A0-A2 and /CS0 + /CS1. In True IDE mode, only three of the address lines of the Compact Flash card are used, in combination with the /CS0 and /CS1 lines which select the "register set". Only either of the /CS0 and /CS1 lines is active (not both at the same time). 2. After a delay of 70 ns (or more), either the /IORD or /IOWR is activated, depending on whether you want to initiate a read or write instruction. The /IORD or /IOWR are the strobes. 3. Another delay, of 165 ns, is needed before inactivating the /IORD or /IOWR lines. At the same time of inactivating the strobe, or immediately before or after inactivating the strobe, you can read or write the data to the D0-D15 lines. 4. Although this is optional, it is recommended that both /CS0 and /CS1 are inactivated at the end of the read or write cycle. You may need another delay here, because a full cycle has also a minimal duration. Instead of a simple idle loop, you may however choose to perform other operations in that time --such as interpreting the data after a read operation, or fetching new data after a write operation. So... again, the problems I'm having are with certain cards and not others. My records of success are 4MB HP - fail, 16MB Kodak - strange behavior/fail, 512MB Simple Technology - fail, SanDisk 1GB - works. I'm just trying to solicit input from anyone who might know a tidbit like "don't try that with cards under 32MB" or some other such nugget of wisdom. I brought up the 8-bit mode thing because it's an unusual use of the CF card and might be relevant. Thanks, -ethan