8" description pc floppy 2 side select 32 10 seek complete n/c 12 restore " 14 eject " 20 index 8 22 ready 34 24 motor on 16 26 ds1(drv select) 10 28 ds2 12 30 ds3 14 32 ds4 6 34 step dir 18 36 step pulse 20 38 write data 22 40 write gate 24 42 track 0 26 44 write protect 28 46 read data 30 all other even pins are not connected all odd pins are earth/ground
With some 'wire weaving' in the ribbon cable - going from 50 to 34 - it is quite possible to substitute a 5.25" high density drive for an 8". That is what they were originally designed for, to be a functional replacement for the 8" DSDD.
******************************************************************** The following table is extracted from the CompatiCard manual: Card 34 37 50 8 Inch Drive Signal Name Pin Pin Direction Pin Signal Name ======================================================================== Programmable 2 3 ---> 2 Low Current Index 8 6 <--- 20 Index Drive Select 1/3 12 8 ---> 28 Drive Select 2 Motor Enable 1/3 16 10 ---> 18 Head Load Step Direction 18 11 ---> 34 Direction Select Step Pulse 20 12 ---> 36 Step Write Data 22 13 ---> 38 Write Data Write Enable 24 14 ---> 40 Write Gate Track 0 26 15 <--- 42 Track 0 Write Protect 28 16 <--- 44 Write Protect Read Data 30 17 <--- 46 Read Data Select Head 1 32 18 ---> 14 Side Select Connect odd number pins of 34 pin connector to odds of 50 pin connector Connect pins 21/37 of the DB-37 to all the odd pins on 50 pin connector ************************************************************************
The interface on 8" drives and 5 1/4" drives are essentially the same. The 34 lines on a typical 5 1/4" controller are sufficient to control most 8" disk drives using soft-sectored disks. Here, then, is a diagram for a basic conversion cable to allow con- nection of an 8" drive to an IBM-compatible, AT-style (high density) controller. This diagram also works in the other direction--that is, to attach high-density 5 1/4" drives to an 8" controller. 8" disk drive PC-AT style controller Based on Shugart SA-851 Grnd. Sig. Sig. Name Sig Name Sig Grnd 1 2 Double/High Density ->> >>- Write Current Switch/ 2 1 Active Read Compensation User Customizable I/O pins 4 3 " " " " 6 5 33 34 **Ready ---------------<<------------ True Ready 8 7 <<-------------#Two Sided 10 9 33 34 **Disk Change ---------<<----------- Disk Change 12 11 31 32 Side 1 Select ------->>-----------#Side Select 14 13 3 4 In Use/Open --------->>---------------- In Use 16 15 15 16 *Motor On ------------>>------------- Head Load 18 17 7 8 Index ---------------<<----------------- Index 20 19 33 34 **Ready ---------------<<----------------- Ready 22 21 <<---------------##Sector 24 23 9 10 Drive Select 0 ------>>-------- Drive Select 1 26 25 11 12 Drive Select 1 ------>>-------- Drive Select 2 28 27 13 14 Drive Select 2 ------>>-------- Drive Select 3 30 29 5 6 Drive Select 3 ------>>-------- Drive Select 4 32 31 17 18 Direction Select ---->>------ Direction Select 34 33 19 20 Step ---------------->>------------------ Step 36 35 21 22 Write Data ---------->>------------ Write Data 38 37 23 24 Write Gate ---------->>------------ Write Gate 40 39 25 26 Track 00 ------------<<-------------- Track 00 42 41 27 28 Write Protect -------<<--------- Write Protect 44 43 29 30 Read Data -----------<<------------- Read Data 46 45 <<------##Separation Data 48 47 <<-----##Separation Clock 50 49 Notes: * - This has not been tested by me. It seems to be a logical substitution since the vast majority of 8" drives have continuously running spindles and instead of MOTOR ON require a HEAD LOAD signal. Also, I assume that a controller sends MOTOR ON before a DRIVE SELECT (my 8" controller will send HEAD LOAD before DRIVE SELECT). **- Most 5 1/4" disk drives do not provide a READY signal but send a DISK CHANGE signal on line 34 of the interface. An 8" drive has provisions for both signals. Likewise, most AT-style controllers expect a DISK CHANGE signal on line 34, so lines 33 and 34 should be connected to lines 11 and 12 of the 8" disk connector. Also, some 8" drives provide a TRUE_READY signal which is more useful than the standard READY. # - Unused on single sided drives (SA-800/801). ##- Used only on hard-sector configured drives (SA-801/851). Some 5 1/4" disk drives have the option of providing _either_ DISK CHANGE _or_ READY on line 34 (in particular, the TEAC FD55R series). Some 8" disk controllers do not care about the DISK CHANGE signal, but must have the READY signal. If you are attaching a high-density 5 1/4" drive to an 8" controller, you may get away with making the drive always ready by shorting lines 21 and 22. I have heard that this may cause a few re-tries when switching sides, but it works fine for me. If your drive offers a READY signal that your controller can deal with, by all means use it. The MOTOR ON/HEADLOAD dilemma may also have an alternate solution if you are connecting 5 1/4" drives to an 8" controller. Some 5 1/4" drives permit motor turn-on by means other than the MOTOR ON signal. For example, the TEAC FD55R series of drives may be configured to turn the motor on based on the state of the IN USE light. The IN USE light can, in turn, be set to turn on only on drive select. Thus selecting the drive automatically turns on the motor and neither a MOTOR ON or IN USE signal need be present. John D. Baker ->An Apple ZCPR3 nut // 8 January 1991 Revised 12 March 1992 Annotated (#,##) by Don Maslin 17 Oct 1995
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