C= Commodore UPDATE



              ADDENDUM:        PART NUMBER 320967
              AFFECTS:         floppy Disk User’s Manual
                               Part Number 320899, October 1980

              



              
              I.8050/8250 Drive Types


              
              
                 Commodore now supplies 8050 and 8250 disk systems
                 with drives from either Micropolis or Tandon
                 Corporations.     The   Floppy    Manual   (320899)
                 describes disk functions using Micropolis drives.
                 Operations with Tandon drives are identical with
                 Micropolis drives except for the loading of the
                 disk.
              



              
                  A.    Drive Identification
              
                    The Micropolis drive is identified by a green
                    LED mounted ABOVE the disk loading slot. The
                    Tandon drive has a red LED mounted BELOW the
                    loading slot.
              
                  B.    Disk loading/unloading:
              
                    1. Micropolis
              
                       The Micropolis drive incorporates circuits to
                       activate the drive motor as the disk is
                       lowered. For this reason the door must not
                       be "teased" as this will cause a misseating
                       of the disk. The recommended procedure is to
                       insert the disk and press the door latch
                       firmly down without hesitation.
              
                    2. Tandon
              
                       Two versions of the Tandon drive are
                       supplied. The versions are identical
                       externally, however the later version has a
                       door switch included to activate the drive
                       motor to aid in seating the disk.
              
                       The version may be determined by listening
                       closely as the drive door is closed. The
                       later version is identified by the sound of
                       the drive motor being activated as the door
                       is closed. The earlier version will not
                       activate the motor.
              
                       To properly seat a disk in earlier drives,
                       the door should be "teased" a couple of times
                       before final closing. In later drives,
                       proper seating will occur only when the door
                       is closed without the. teasing procedure.

              
              
              
              
              
              II.  Device Number Alteration
              
                 Occasionally it is desirable to alter the device
                 number (primary address) of a disk system. As
                 assembled at the factory, each CBM floppy disk
                 system has a primary address of’8. The following
                 program will allow the change of the address to
                 other values as shown in the table.
              
              
                 The program to change the device number (primary
                 address) is:
              
              
                       10 OPEN 15,CH,15
                       20 PRINT#15 , "M-W"CHR$ (LB)CHR$(0)
                           CHR$(2)CHR$(NA+32)CHR$(NA+64)
              
                       WHERE:   CH = Current primary address
                                     (8 at Pwr On/Reset)
                                NA = New Address (table below)
                                LB = Address of IEEE address
                                     (table below)
    
		                 SYSTEM   ALLOWED RANGE               LB
                                 OF NEW ADDRESS
                        2040/3040      8-15                  50
                        4040           8-15                  12
                        8050           8-15                  12
                        8250           8-15                  12
              
                 NOTE:   1. The address change is in effect only
                 until the system is reset either by the primary AC
                 power switch to the disk system or to the CBM
                 computer, or by the execution of the user reset
                 vector "UJ" (described in the manual page 52/53).
              
                 NOTE:   2. Remember to append the unit number
                 parameter (Udn) to all BASIC 4.0 disk commands as
                 the default is to unit 8.