╘HE 1541 COMPATIBLE ═╙─ DISK DRIVES SUPPLIED BY ═╙─ ╙YSTEMS ╔NC, ARE A RECENT ADDITION TO ├OMMODORE HARDWARE. ┬ECAUSE OF THEIR ADVANCED FEATURES--INCLUDING HIGH SPEED FORMATTING AND RESISTANCE TO MISALIGNMENT AND OVERHEATING--THE ═╙─ DRIVES ARE OFTEN SELECTED FOR HEAVY DUTY DISK SERVICE. ╘HE DUAL ╙─-2 MODEL WITH ITS HIGH SPEED DISK DUPLICATION ROUTINE IS PREFERRED FOR DATABASE OR RELATED APPLICATIONS WHERE FREQUENT DATA DISK BACKUPS ARE NEEDED.
═╙─ DRIVES ARE EQUIPPED FOR OPTIONAL USE IN PARALLEL MODE (WITH AN ╔┼┼┼ INTERFACE) FOR HIGH SPEED DISK COMMUNICATIONS. ═OST ═╙─ DRIVES ARE USED WITH THE ├-64 OR ├-128. ┬ECAUSE OF THE ╔┼┼┼ CONNECTION, SOME ARE USED WITH THE ┬-128 OR ╙UPERPET.
═╙─ DRIVES ALSO EMPLOY INNOVATIVE HARDWARE TECHNOLOGY. ╘HE HEART OF THE DRIVES IS A ╥OCKWELL ╥6511╤ MICROPROCESSOR WHICH USES STANDARD 6502 OP CODES, BUT INCLUDES BUILT-IN TIMERS AND DATA PORTS. ╘HE ╥6511╤ REPLACES THREE CHIPS--A 6502 AND TWO 6522'S--IN THE 1541. ╘HE DRIVES ALSO USE ╘OKYO ┼LECTRIC ╫ORKS (╘┼├) ═ODEL ╞┬-501 INTELLIGENT DRIVE MECHANISMS, THEREBY REDUCING ─╧╙ PROCESSING.
╘HE IMPROVED FEATURES REQUIRED MODIFICATIONS IN ─╧╙. ═╙─ ─╧╙ 2.3 RESEMBLES ├OMMODORE ─╧╙ 2.6, BUT ADDRESSES ARE DIFFERENT. ╘HE MEMORY MAP THAT FOLLOWS WAS ASSEMBLED BY MEMBERS OF THE ═╙─ ╔NFORMATION ┼XCHANGE TO ENCOURAGE OPTIMUM USE OF ═╙─ FEATURES. ╘HE ARRANGEMENT FOLLOWS THAT OF THE ├OMPLETE ├OMMODORE ╔NNER ╙PACE ┴NTHOLOGY BY ╦ARL ╩╚ ╚ILDON (╘RANSACTOR). ╙UBROUTINES HAVE BEEN NAMED ACCORDINGLY AND ARE CROSS-REFERENCED TO THE CORRESPONDING 1541 ─╧╙ LOCATION. ╙UBROUTINE NAMES PUBLISHED IN THE ═╙─ ╙ERVICE ═ANUAL (═╙─ ╙YSTEMS ╔NC) HAVE ALSO BEEN USED WHERE POSSIBLE. ┴ DETAILED EXPLANATION OF THE FUNCTIONS OF ├OMMODORE ─╧╙ IS PUBLISHED IN ╔NSIDE ├OMMODORE ─╧╙ BY ╥ICHARD ╔MMERS AND ╟ERALD ╟. ╬EUFELD (─ATAMOST).
═UCH OF THE ═╙─ ZERO PAGE IS RESERVED FOR THE ╥6511╤ AND ITS DATA PORTS. ┴LL 1541 ZERO PAGE AND PAGE ONE ╥┴═ LOCATIONS ARE DIFFERENT IN ═╙─ ─╧╙. ═ANY OF THE EQUIVALENTS ARE FOUND ON PAGES 4├ AND 4┼. ╘HE DATA BUFFERS BEGIN AT $4000.
╘O IMPROVE SOFTWARE COMPATIBILITY, SOME ADDRESSES IN "═-╫", "═-┼", AND "═-╥" COMMANDS ARE TREATED AS 1541 ADDRESSES. ╘HEY ARE CONVERTED BY ─╧╙ TO THEIR ═╙─ EQUIVALENTS. ╔N THE MEMORY MAP THE CONVERTED LOCATIONS ARE MARKED WITH A FOOTNOTE. ╘HE CONVERSION OCCURS AT $├─05 USING A CONVERSION TABLE AT $├├┼╞.
┬OTH THE SINGLE ╙─-1 AND DUAL ╙─-2 MODELS USE ═╙─ ─╧╙ 2.3. ─╧╙ DISTINGUISHES THE MODELS BY RESPONSE FROM DRIVE 1. ╘HE ╙─-2 IS ALSO EQUIPPED WITH EXTRA ╥┴═. ╘HE ╙─-1 IS SUPPLIED WITH 4╦; THE ╙─-2 IS SUPPLIED WITH 6╦. ┬OTH MODELS MAY BE EQUIPPED WITH UP TO 8╦. ╫HEN PRESENT, THE EXTRA ╥┴═ IS LOCATED AT $5000 AND ABOVE.
╘HE HIGH SPEED DISK DUPLICATION ROUTINE OF THE ╙─-2 USES THE EXTRA ╥┴═ FOR INTERNAL DATA STORAGE. ╘HE DISK DUPLICATION ROUTINE IS LOCATED AT $├7├6 AND USES A TABLE OF ╥┴═ ADDRESSES AT $├928.
─╧╙ USES SEPARATE ROUTINES FOR ╔┼┼┼ AND SERIAL COMMUNICATIONS. ╘HE ╔┼┼┼ ROUTINES ARE VECTORED FROM $4├╞2 (╓┴╘╬╔) AND BEGIN AT $╞0├┴. ╘HE SERIAL BUS ROUTINES ARE VECTORED FROM $4├╞4 (╙┼╥╓┼├) AND BEGIN AT $┼┼┼6. ═╙─ RECOMMENDS ╙┼╥╓┼├ AS A BRANCH POINT FOR USER COMMUNICATIONS ROUTINES. ╦EY ╔/╧ PORT DATA ARE SUMMARIZED IN ╘ABLE 3.
╘HE HIGH SPEED FORMATTING ROUTINE BEGINS AT $╞820. ┴ DETAILED DISASSEMBLY OF THIS ROUTINE IS PUBLISHED IN THE ═╙─ ╙ERVICE ═ANUAL. ╘HE ROUTINE MAY BE MODIFIED AND IMPLEMENTED AT $4800, ACCORDING TO ═╙─.
╘HE ╥6511╤ MICROPROCESSOR USES EXTRA OP CODES IN ADDITION TO STANDARD 6502 CODES. ╘HEY ARE ╙═┬ (TWO BYTES; SETS ONE BIT OF THE SPECIFIED ZERO PAGE LOCATION TO "1"), ╥═┬ (TWO BYTES; RESETS ONE BIT TO "0"), ┬┬╙ (THREE BYTES; TESTS ONE BIT OF THE ZERO PAGE ADDRESS SPECIFIED IN BYTE TWO AND IF "1" BRANCHES TO THE RELATIVE ADDRESS SPECIFIED BY BYTE THREE; IF THE BIT IS "0", NO BRANCH OCCURS); AND ┬┬╥ (THREE BYTES; BRANCHES IF THE BIT IS "0").
╘HE BIT TO BE SET OR TESTED IS SPECIFIED BY THE OP CODE AS FOLLOWS--
╙UBMITTED BY ╘HE ═╙─ ╔NFORMATION ┼XCHANGE, 2705 ╚ULMAN ╙T, ╘ERRE ╚AUTE, ╔╬ 47803 FROM CONTRIBUTIONS BY ╫ILLIAM ╫ENTZ OF ┴LBUQUERQUE, ╬═ AND ╨AUL ╥USHTON OF ┼DMONTON, ┴LBERTA. ┴NY CORRECTIONS, ADDITIONS, OR COMMENTS SHOULD BE SUBMITTED TO THE ┼XCHANGE.
