[ 53280,0:53281,0:646,(162):"":" USE LYNX TO DISSOLVE THIS FILE":10 1 *LYNX BY CBMCONVERT 2.0* 2 ENSITY ISPLAY 62 P 129 ECH ONT 34 P 27 Density Display] 2=PRG formatted GEOS file V1.0|"@D"@D"@D"@D|` =j $!$'( 0?Write Image V2.1geoWrite V2.1DENSITY LEVEL DISPLAY (C) 1990,Wesley J. Wiese.Make your own DLD for 1541,1571 and compatibles.x] pppppppppNHDENSITY LEVEL DISPLAYN LEGAL NOTICES `````````@All documents in thisN@ Density Level Display Nseries are Copyright (C) 1989, 1990 Wesley J. Wiese. All rights reserved. Any and all consequences resulting from the use of these documents is the expressed responsibility of the user.The author will not be held liable and does not imply any warranty or guarantee. The author does certify that all information presented in these documents was correct, to his knowledge, at the time of distribution of these documents. All documents in thisN@ Density Level DisplayN series are the sole property of the author, who retains all copyrights and patents to the material presented. All documents in this N@Density Level DisplayN series will not be distributed or reproduced or stored in any retrieval system without the prior permission of the author.N@ (NThis document appeared first in the Southern Maine Commodore User's Group (N@S.M.C.U.GN.) newsletter, N@C-LINKN, Volume 6, Issue 5, May 1989.N@)N First let's look at the way Commodore DOS uses densitys for GCR (Group Coded Recording). Using a programmable divide by N counter off of a 16 Megahertz clock, the speed at which the data is written to (or read from) a disk can be altered. This is needed because the tracks get physically smaller towards the center of the hub so the frequency at which the data is being written to or read from the disk has to be decreased to keep some normalcy to the flux density of the disk. Normally there are four densitys, one being the most dense, four the least. Many commercial programs use only the first two densitys to cram more information on the higher tracks. Using a small internally or externally mounted hardware device we can read the density, via 7-segment LED display, that is being written to or read from the disk. Using the 16 Megahertz crystal clock module as a base reference, the divide by N counter can be altered via software to speed up or slow down the clock frequency at which each byte of data is transformed into 8 bit serial data then passed to the write amplifiers. This frequency varies from 1.2307 Megahertz on the outer tracks (density 1) to 1 Megahertz on the inner tracks (density 4). The software location for this control is 1C00 Hex in the drive, bits 5 and 6. This is Port B of one of the 6522's VIA (N@VNersatile N@INnterface N@ANdaptor) chip. The DOS (N@DNisk N@ONperating N@SNystem) dedicates this chip to transferring data to and from the the disk. It also has hardware control of the disk drive motor, density levels, stepper motor, sync bytes, write protect sensor and drive activity LED. The N@Density Level DisplayN is a piece of hardware that utilizes bits 5 and 6 of port B of this 6522 VIA. It monitors these bits independent of the software controlling them, whether that be Commodore DOS or a commercially protected program. The device consists of a Nor gate, an Exclusive-or gate, a BCD decoder/driver, 330 @ resistors and a 7-segment LED. Bit manipulation is needed to transpose the 2 bits of data into a easily readable form. `````````N@Bit Manipulation Truth Table `(````` Board Inputs IC3 Inputs `(@x` Tracks DS0 DS1 ''1'' ''2'' ''4'' Decimal Out `(H` N31-35 0 0 0 0 1 4 25-30 1 0 1 1 0 3 18-24 0 1 0 1 0 2 1-17 1 1 1 0 0 1 `````````NHDensity Level Display SchematicN `````````@ `````````C@NHDensity Level Dislay Layout N@Bottom ViewN `````````#XANHDensity Level Display Guide N@Top ViewN `````````8pBNHParts List `8``````` NIC1- 74LS02 // IC2- 74LS86 // IC3- 74LS47 // R1-R7- 330@ 1/4 watt resistors LED1- MAN6760 or equivilent common anode 7-segment display 12 inches of 4 conductor ribbon cable ````````` NHConnection Guide    N@Disk Drive +5 Volts Power Ground DS0 DS1 1541 12'' Board NPin 14 IC-UG4 Pin 7 IC-UG4 Pin 15 IC-UCD4 Pin 16 IC-UCD4N@ 1541 9'' Board NPin 14 IC-UD2 Pin 7 IC-UD2 Pin 15 IC-UC2 Pin 16 IC-UC2N@ 1541 6'' Board NPin 14 IC-UA1 Pin 7 IC-UA1 Pin 15 IC-UC3 Pin 16 IC-UC3N@ 1541-II NPin 14 IC-U1 Pin 7 IC-U1 Pin 15 IC-U8 Pin 16 IC-U8N@ 1571 NPin 14 IC-U8 Pin 7 IC-U8 Pin 15 IC-U4 Pin 16 IC-U4N@ 128D 1571 NPin 14 IC-U113 Pin 7 IC-U113 Pin 15 IC-U104 Pin 16 IC-U104N@ Excelerator + NPin 14 IC-U12 Pin 7 IC-U12 Pin 15 IC-U9 Pin 16 IC-U9N@ Blue Chip 1541N Pin 14 of the Pin 7 of the Pin 15 of 6522 Pin 16 of 6522 74LS10 to the 74LS10 to the between the other between the other left of 6522's left of 6522's 6522 and 6502 6522 and 6502NDATE TIME N@Density Level Display (C) 1989,1990 Wesley J. Wiese NPage PAGECm000> 00 0< 0 ) ) 1)< 00)`0)@00 @c`18 @f`$ @g@ @``@ 1ϟg@`@  㹙@ @  `@ @  c @   f8 p@  f>f8@ f0@p@` < @a 8@c ?@ 8@?<@x| <3 @ c` c6`8  x 6 ` 8 c6  `? c6 `@ `  c6 `@  | ( x c3<@ `$  @ D? @@ `B@ @  xB @ @  @  @ ?@p@ 8 s   a8G 8  @ a @l x (@ x1@@@@ `$@ 1@~@ D?@@@  `B@@@a@ @  |B@@a@@`@@@s@@x@@@@ @@@ @@@  @@8@ x (@@ @@ `$@A8   D?@A  `B@@A  B@A @@A 06@@A >f @A 3~@A 3x @A    (@C  `$@C|? 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