Path: utzoo!mnetor!uunet!portal!cup.portal.com!John_-_DeBert From: John_-_DeBert@cup.portal.com Newsgroups: comp.sys.cbm Subject: Re: Need 1541 info Message-ID: <4587@cup.portal.com> Date: 18 Apr 88 08:26:07 GMT References: <5314@pyr.gatech.EDU> Organization: The Portal System (TM) Lines: 143 XPortal-User-Id: 1.1001.1968 In answer to your questions about using the 1541 with your homebrew machine that you put out on USENET: 1. The transfer rate is listed by a couple of sources as 400 bits/seconds. But a file of 254 bytes or less loads in less than one second. I suspect that they mean bytes/second. 2. I am mailing data on the serial bus connector. Of the five available signals one is not used - bus SRQ - by the 1541. 3. Books about the 1541: 1. The New Anatomy of the 1541 Disk Drive By Lothar Englishce & Norbert Szczepanowski ISBN 0-916439-01-1 Published by Abacus Software P.O. Box 7211 Grand Rapids, MI 49510 Contaians assembly listings of 1541 operating system ROM routines & info on using the 1541 with Commodore Computers.The assembly listings can be used to calculate the serial bus timing based on the 1541's 1 MHz clock. 2. InsIde Commodore DOS by Drs. Richard Immers, Ph.D. & Gerald G. Neufeld, Ph.D. ISBN 0-8359-3091-2 Published by: Datamost 20660 Nordhoff St. Chatsworth, CA 91311-6152 (818) 709-1202 Contains a very detailed description of the 1540/1541 operating system ROM routines, including technical information on the operation of the drive. There are no assembly listings. The above books should give you plenty of information on the 1541, enough to let you use the drive with your machine. 4. For info on the 1541 hardware: Commodore 1541 Troubleshooting & Repair Guide by Michael G. Peltier ISBN 0-672-22470-4 published by: Howard W. Sams & Co. 4300 West 62nd St Indianapolis, IN 46268 5. The bus interface uses open collector outputs with a 1.0K-ohm pullup. 6. Suggest checking the schematic in the back of the C-64 Programmers Reference Guide for details on the bus interface. Following is some other interesting & pertinent details: file: txt.filatr03 871129 Commodore DOS file attributes Detail of the file attribute byte: 7 6 5 4 3 2 1 0-> BIT NOTES: X X X X X X X X : : : : : : : : (0 = low or clear) 1. A scratched file's attribute byte : : : : : : : : (1 = high or set ) is: 00000XXX : : : : : : : : (X = "don't care") 2. For some DOS versions, if a : : : : : : : : scratched file has it's lock : : : : : ------> FILE TYPE set, it will appear in the : : : : : directory as 'DEL<'. While it : : : : : 000 DEL Deleted file may appear in the directory, : : : : : 001 SEQ Sequential file the sectors assigned to the : : : : : 010 PRG Program file file have been freed for use : : : : : 011 USR User file by subsequent file writes. : : : : : 100 REL Relative file Attempting to read such a file : : : : : 1XX --- Invalid may cause the drive to hang, or : : : : : cause some other problem that : : : ----------> Reserved will require the drive to be : : : reset or turned off. : : ------------> @ flag 3. DOS does not support the locking : : 1 replacement file and unlocking of files. To lock : : or unlock a file, the file : --------------> Lock flag attribute byte must be directly : 1 Locked file edited, using a utility such as : DISK DOCTOR or by using direct ----------------> Valid flag access commands. (For more 1 Valid file information on direct access, see 'Inside Commodore DOS,' ISBN 0-8359-3091-2, by Datamost. *nb CBM serial bus commands *nb orig 5 Feb 1988 *cn1 Commodore Serial Bus Command Byte Structure By J. DeBert *cn0 Commodore's serial bus protocol attempts to follow the IEEE-488 convention as closely as possible. The command byte convention necesarily differs somwhat, however, due to the bus structure. Command Byte: X X X X X X X X : : : : : : : : : : : - - - - - -> Device Address: : : : : : : 0 - 31 expressed in binary. : : : : : : - - - - - - - - -> Command: 000 001 Listen (except... 00111111, the command to device 31 to listen is used as general unlisten.) 010 Talk (with same exception as Listen command.) 011 secondary address (0-31) 100 101 110 111 close (secondary address) The Commodore BASIC does not support the use of devices with an address from 0 to 3, however, the serial bus KERNAL routines may be used to select such devices. KERNAL routines OPEN cannot be used to access any device with an address less than 4 on the serial bus. It is possible to expand on the serial bus system here using your own KERNAL routines. *fp0 Hope this helps. Have fun, John_-_DeBert@cup.portal.com CIS: 75530,347 Telex: 6502636614 slug-express: P.O. Box 51754, Pacific Grove, CA, 93950-6754, USA, Terra