tre@sdcarl.UUCP (Tom Erbe) (01/14/86)
I would like to know what kind of protocol the DMA port on
the atari 520st uses. Since it is the only high speed port on the
machine, it would be nice if it was a general purpose port and not
completely tied to hard-disk type devices. Could someone with the
developer's kit help me out here?
Thanks in advance,
thomas r. erbe
{ucbvax,ihnp4,akgua,hplabs,sdcsvax}!sdcarl!tre
--
thomas r. erbe
{ucbvax,ihnp4,akgua,hplabs,sdcsvax}!sdcarl!trerb@ccivax (01/21/86)
> > I would like to know what kind of protocol the DMA port on > the atari 520st uses. Since it is the only high speed port on the > machine, it would be nice if it was a general purpose port and not > completely tied to hard-disk type devices. Could someone with the > developer's kit help me out here? > One magazine article and some E-mail directly to me indicates that Atari will (has) implement(ed) X3T9(SCSI) protocol in the new ROM (confirmations?). Appearently, there is a small expansion box required (the DMA port does not support full SCSI arbitration). SCSI has provisions for DISK, Printer, CPU-CPU communications. SCSI even has provisions for remote file/systems with high levels of intellegence (Like I/O to-from a UNIX box) with features like 'search for pattern', though not all peripherals support it. The SCSI standard is actually "ANSII Standard X3T9-2" and can be obtained from engineering libraries, the National Bureau of Standards, ANSI, or Mini-Micro Systems. MMS provides this on a 5 1/4" floppy in IBM-PC format. The others provide it printed. Many are expecting (hoping) that SCSI will replace RS-232 as the general purpose interface standard. Full SCSI (I don't know what Atari's final plans are), allows a very low cost network of up to 8 devices. Any combination of printers, CPU's and Drives (SCSI), may be used. SASI drives may be used as well, but probably not in network configuration. SCSI is intended to be a true 'Generic Buss', eliminating normal interface problems such as timing, protocol, and data-bus width (SCSI is ALWAYS 8 bits wide). If Atari implements FULL SCSI, the interfacing problems associated with drives and special peripherals are reduced significantly. Full SCSI is even simpler than GPIB protocol. The first request is "What Are You", (Inquiry). Then read block 0, to boot. A quick summary is as follow Basic Format of Commands(Transactions) Bit | 7 | 6 | 5 | 4 | 3 | 2 | 1 | 0 | Byte| | | | | | | | | ------------------------------------- 0 | Operation Code | 1 |Logial unit| Command Dependent | 2 | Parm (usually MSB) | 3 | Parmameter | 4 | Parameter (usurally LSB) | 5 | VdnrU*|Reserved |Flag | | ------------------------------------- 6-?? Optional Data | ------------------------------------- Operation Meaning Code 00 Test unit Ready (Optional) 01 Rezero Unit (Optional) 02 (Vendor Provides Support) 03 Request Sense (Mandatory) 04 Format Unit (Mandatory) 05 (Vendor Provides Support) 06 (Vendor Provides Support) 07 Reassign Blocks (Optional) 08 Read (Block:24,Length in blocks:8) (Mandatory) 09 (Vendor Provides Support) 0A Write (Block:24,Length in blocks:8) (Mandatory) 0B Seek (Optional) 0C (Vendor Provides Support) 0D (Vendor Provides Support) 0E (Vendor Provides Support) 0F (Vendor Provides Support) 10 (Vendor Provides Support) 11 (Vendor Provides Support) 12 Inquiry (Vendor provided support gets loaded here) 13 (Vendor Provides Support) 14 (Vendor Provides Support) 15 Mode Select (Optional) 16 Reserve (Optional) 17 Release (Optional) 18 Copy (Optional) 19 (Vendor Provides Support) 1A Mode Sense (Optional) 1B Start/Stop Unit (Optional) 1C Recieve Diagnostic Results 1D Send diagnostic 1E Prevent/Allow Medium Removal 1F (Reserved for future use)