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*
** FLEX 9 DISK DRIVERS
** FOR SINGLE/DOUBLE SIDED 5" DRIVES ONLY.
** USING FD1771.
** SIDES MAY BE TREATED AS SEPERATE DISKS.
**
** BY J.E.KENT   1 JAN 1982
*
*
** F.D. CONTROLLER
*
DRVREG EQU   $E014
MOTOR  EQU   %10000000
SIDESL EQU   %01000000
DRIVSL EQU   %00000001
CMDREG EQU   $E018
TRKREG EQU   $E019
SECREG EQU   $E01A
DATREG EQU   $E01B
*
** FD1771 DISK CONTROLLER INSTRUCTIONS
*
** TYPE I INSTRUCTIONS:
*
IREST EQU $00 RESTORE (SEEK TRACK 0)
ISEEK EQU $10 SEEK TRACK
ISTEP EQU $20 STEP ONE TRACK (IN/OUT)
ISTIN EQU $40 STEP IN ONE TRACK
ISTOUT EQU $60 STEP OUT ONE TRACK
*
** BIT FIELDS FOR TYPE I INSTRUCTIONS
*
SMR6 EQU $00 6MSEC STEPPING RATE
SMR12 EQU $01 12 MSEC STEPPING RATE
SMR20 EQU $02 20 MSEC
SMR40 EQU $03 40 MSEC
*
BVERIF EQU $04 VERIFY BIT (1=ON)
BHDLD EQU $08 HEAD LOAD (1=LOAD HEAD AT BEGINING)
BUPDAT EQU $10 UPDATE TRACK REGISTER (1=TRUE)
*
** TYPE II INSTRUCTIONS
*
IREAD EQU $80 READ SECTOR
IWRITE EQU $A0 WRITE SECTOR
*
** BIT FIELD FOR TYPE II
*
BDAMFB EQU $00 $FB DATA ADDRESS MARK
BDAMFA EQU $01 $FA DATA ADDREES MARK
BDAMF9 EQU $02 $F9 DATA ADDRESS MARK
BDAMF8 EQU $03 $F8 DATA ADDRESS MARK
BEHLD EQU $04 ENABLE HLD & 10 MSEC DELAY (1=ACTIVE)
BBLEN EQU $08 BLOCK LENGTH (1=IBM FORMAT 128 - 1024 BYTES)
BMREC EQU $10 MULTIPLE RECORD (0=SINGLE, 1=MULTIPLE)
*
** TYPE III INSTRUCTIONS
*
IRDADD EQU $C4 READ ADDRESS
IRDTRK EQU $E4 READ TRACK
IWRTRK EQU $F4 WRITE TRACK
*
** BIT FIELD TYPE III (READ TRACK ONLY)
*
BSYNC EQU $01 SYNCRONIZE FLAG (0=SYNC TO AM)
*
** TYPE IV NSTRUCTION
*
IFINTR EQU $D0 FORCE INTERRUPT
*
** FORCED INTERRUPT BITS (TYPE IV INSTRUCTION)
*
FI0 EQU $01 NOT READY TO READY TRANSITION
FI1 EQU $02 READY TO NOT READY TRANSITION
FI2 EQU $04 INDEX PULSE
FI3 EQU $08 EVERY 10 MSEC
*
** DISK DRIVER PATCHES
*
       ORG   $DE00
*
** JUMP TABLE TO DISK DRIVERS
*
READ   JMP   READSC
WRITE  JMP   WRITSC
VERIFY JMP   VERIF1
RESTOR JMP   RESTR1
DRIVE  JMP   DRVSEL
DRVRDY JMP   CHKDRV
QUICK  JMP   CHKDRV
COLDDR JMP   INITDR
WARMDR JMP   WARMD1
SEEK   JMP   SEEK1
*
** CURRNT DRIVE NUMBER ($DE1E)
*
CURDRV FCB   $00
*
** HEAD POSITION TABLE ($DE1F)
*
TRKTBL FCB   $00       DRIVE 0
       FCB   $00       DRIVE 1
       FCB   $00       DRIVE 2
       FCB   $00       DRIVE 3
*
** ??? ($DE23)
*
       FCB 0
*
** DENSITY TABLE: ($DE24)
** HOLDS SECTORS/TRACK FOR DRIVE
** 5" SINGLE DENSITY => 10 SECTORS/TRACK
*
DNSTBL FCB 10,10,10,10 ALL MINIS
*
** DRIVE & DISK CHARACTERISTICS
*
* BITS 1,0 STEPPING RATES
* BIT  2   TRACKS/DISK (0=40 TRACK, 1=80 TRACK)
* BIT  3   TRACKS/DRIVE (0=40 TRACK, 1=80 TRACK)
*
BDVTPI EQU $08
BDKTPI EQU $04
DDCTBL EQU *
 FCB BDVTPI+BDKTPI+SMR6
 FCB BDVTPI+BDKTPI+SMR6
 FCB SMR40
 FCB SMR40
*
** DISK DRIVERS
*
* DRIVER INITIATION
*
INITDR LDX   #CURDRV
       LDB   #5
INITD2 CLR   ,X+
       DECB
       BNE   INITD2
WARMD1 RTS
*
* READ ONE SECTOR
*
READSC BSR   SEEK1
       LDA   #IREAD+BBLEN+BEHLD
READ2  ORCC  #$10
*      SEI             DISABLE INTERRUPTS
       STA   CMDREG
       LBSR  DLY47
       LDB   #$00
RDLOOP LDA   CMDREG
       BITA  #$02
       BNE   RDBYTE
       BITA  #$01
       BNE   RDLOOP
       TFR   A,B
       BRA   RDEXIT
*
RDBYTE LDA   DATREG
       STA   ,X+
       DECB
       BNE   RDLOOP
       BSR   WAIT
RDEXIT BITB  #$1C
       ANDCC #$EF
*      CLI
       RTS
*
** WAIT UNTIL CONTROLLER READY
*
WAIT   LDB   CMDREG
       BITB  #$01
       BNE   WAIT
       RTS
*
** SEEK1 TRACK AND SECTOR
** ACCA = TRACK NUMBER
** ACCB = SECTOR NUMBER
*
SEEK1  STB   SECREG    SET SECTOR
       CMPB  #10       DOUBLE-SIDED ?
       BHI   SEEK2     DOUBLE SIDED, FLIP
       LDB   CURDRV    BACK SIDE OF DISK ?
       CMPB  #1        DRIVE 2-3 BACK SIDE
       BHI   SEEK3
       ANDB  #$FF-SIDESL SELECT SIDE 0
       BRA   SEEK4
*
SEEK2  LDB   CURDRV   SELECT SIDE 1
SEEK3  ANDB  #DRIVSL
       ORB   #SIDESL
SEEK4  STB   DRVREG
*
       CMPA  TRKREG    DIFFERENT TO LAST ?
       BEQ   FOUND
       PSHS A          SAVE TRACK NO. ON STACK
*
* IF 80 TRACK DRIVE, & 40 TRACK DISK, FIRST SEEK
* SHOULD NOT UPDATE TRACK REGISTER NOR VERIFY.
*
       SUBA TRKREG  CALC. DIFFERENCE
       TFR  A,B
       PSHS Y
*
** GET STEPPING RATE FROM TABLE
*
       LDY  #DDCTBL
       LDA  CURDRV
       ANDA #$01
       LDA  A,Y
       PULS Y
*
** CHECK DRIVE AND DISK TYPE
*
       BITA #BDVTPI DRIVE TRACK DENSITY = 48 TPI ?
       BEQ  SEEKVU  YES, SKIP
       BITA #BDKTPI DISK TRACK DENSITY = 96 TPI ?
       BNE  SEEKVU  YES, SKIP (DRIVE & DISK MATCH)
*
** HERE IF 40TRACK DISK IN 80 TRACK DRIVE
** USE STEP INSTRUCTIONS TO PREVENT UPDATE OF TRACK REG.
*
       ANDA #$03    LEAVE STEPPING RATE BITS
       TSTB
       BPL  STEPIN
       NEGB
       ORA  #ISTOUT
       BRA  STEPLP
STEPIN ORA  #ISTIN
STEPLP PSHS B
       BSR  SEEK5
       PULS B
       DECB
       BNE  STEPLP
*
** SEEK TRACK WITH VERIFY & UPDATE
*
SEEKVU ANDA #$03    RETAIN STEPPING RATE
       ORA  #ISEEK+BHDLD ($18)
       PULS B          RESTORE DEST TRACK NO.
       STB   DATREG    YES, SEEK1 NEW TRACK
       LBSR  DLY47
SEEK5  STA   CMDREG
       LBSR  DLY47
       BSR   WAIT
       BITB  #$10      CHECK FOR SEEK1 ERROR
FOUND  JMP   DLY47
*
** WRITE SECTOR TO DISK
*
WRITSC BSR   SEEK1
       LDA   #IWRITE+BBLEN+BEHLD ($AC)
WRITE2 ORCC  #$10
*      SEI
       STA   CMDREG
       LBSR  DLY47
       LDB   #$00
WRLOOP LDA   CMDREG
       BITA  #$02
       BNE   WRBYTE
       BITA  #$01
       BNE   WRLOOP
       TFR   A,B
       BRA   WREXIT
*
WRBYTE LDA   ,X+
       STA   DATREG
       DECB
       BNE   WRLOOP
       LBSR  WAIT
WREXIT BITB  #$5C
       ANDCC  #$EF
*      CLI
       RTS
*
** VERIFY SECTOR WRITTEN
*
VERIF1 LDA   #IREAD+BBLEN+BEHLD ($8C)
VERIF2 ORCC  #$10
*      SEI
       STA   CMDREG
       LBSR  DLY47
       LBSR  WAIT
       ANDCC #$EF
*      CLI
       BITB  #$18
       RTS
*
** SEEK TRACK ZERO
*
RESTR1 PSHS  X
       BSR   DRVSEL
       LDX  #DDCTBL
       LDA  CURDRV
       ANDA #1
       LDA  A,X
       ANDA #$03
       ORA  #IREST+BHDLD
       STA   CMDREG
       BSR   DLY47
       LBSR  WAIT
       BITB  #$D8      CHECK FOR ERROR
       PULS  X,PC
*
** SELECT DRIVE
** IX -> FCB
** ACCA =  NEW DRIVE NUMBER
*
*  SAVE OLD TRACK NUMBER IN TABLE
*  AND SET UP TRACK FOR NEW DRIVE
*
*
DRVSEL LDA   3,X
       CMPA  #3
       BLS   DRSEL1
       LDB   #$0F      SET ERROR VALUE
*       SEC
       ORCC  #$01
       RTS
*
* SAVE TRACK POSITION OF PREVIOUS DRIVE
*
DRSEL1 BSR   PNTDRV
       LDB   TRKREG
       STB   ,X
*
* SELECT NEW DRIVE
*
DRSEL3 STA   CURDRV    MAY BE 0 - 3
       CMPA  #1
       BLS   DRSEL4    ONE DIRECTORY ?
       ANDA  #DRIVSL   ROUND OFF
       ORA   #SIDESL   SELECT SIDE 1
DRSEL4 STA   DRVREG
*
* RESTORE LAST TRACK POSITION FOR THIS DRIVE
*
       BSR   PNTDRV
       LDA   ,X
       STA   TRKREG
       BSR   DLY47
       BRA   OK
*
** CHECK IF DRIVE READY
*
CHKDRV LDA   3,X
       CMPA  #3
       BLS   OK
       LDB   #$80
*       SEC
       ORCC  #$01
       RTS
 
OK     CLRB
*       CLC
       ANDCC #$FE
       RTS
*
* POINT TO TRACK TABLE ENTRY FOR THIS DRIVE
*
PNTDRV LDX   #TRKTBL
       LDB   CURDRV
       ANDB   #DRIVSL
       ABX
       RTS
*
** DELAY ROUTINE
*
DLY47  LBSR  DLY19
DLY19  LBSR  DLY5US
DLY5US RTS
       END
 

Line No.	Rev	Author	Line
1	42	davidgb	`*`
2			`** FLEX 9 DISK DRIVERS`
3			`** FOR SINGLE/DOUBLE SIDED 5" DRIVES ONLY.`
4			`** USING FD1771.`
5			`** SIDES MAY BE TREATED AS SEPERATE DISKS.`
6			`**`
7			`** BY J.E.KENT 1 JAN 1982`
8			`*`
9			`*`
10			`** F.D. CONTROLLER`
11			`*`
12			`DRVREG EQU $E014`
13			`MOTOR EQU %10000000`
14			`SIDESL EQU %01000000`
15			`DRIVSL EQU %00000001`
16			`CMDREG EQU $E018`
17			`TRKREG EQU $E019`
18			`SECREG EQU $E01A`
19			`DATREG EQU $E01B`
20			`*`
21			`** FD1771 DISK CONTROLLER INSTRUCTIONS`
22			`*`
23			`** TYPE I INSTRUCTIONS:`
24			`*`
25			`IREST EQU $00 RESTORE (SEEK TRACK 0)`
26			`ISEEK EQU $10 SEEK TRACK`
27			`ISTEP EQU $20 STEP ONE TRACK (IN/OUT)`
28			`ISTIN EQU $40 STEP IN ONE TRACK`
29			`ISTOUT EQU $60 STEP OUT ONE TRACK`
30			`*`
31			`** BIT FIELDS FOR TYPE I INSTRUCTIONS`
32			`*`
33			`SMR6 EQU $00 6MSEC STEPPING RATE`
34			`SMR12 EQU $01 12 MSEC STEPPING RATE`
35			`SMR20 EQU $02 20 MSEC`
36			`SMR40 EQU $03 40 MSEC`
37			`*`
38			`BVERIF EQU $04 VERIFY BIT (1=ON)`
39			`BHDLD EQU $08 HEAD LOAD (1=LOAD HEAD AT BEGINING)`
40			`BUPDAT EQU $10 UPDATE TRACK REGISTER (1=TRUE)`
41			`*`
42			`** TYPE II INSTRUCTIONS`
43			`*`
44			`IREAD EQU $80 READ SECTOR`
45			`IWRITE EQU $A0 WRITE SECTOR`
46			`*`
47			`** BIT FIELD FOR TYPE II`
48			`*`
49			`BDAMFB EQU $00 $FB DATA ADDRESS MARK`
50			`BDAMFA EQU $01 $FA DATA ADDREES MARK`
51			`BDAMF9 EQU $02 $F9 DATA ADDRESS MARK`
52			`BDAMF8 EQU $03 $F8 DATA ADDRESS MARK`
53			`BEHLD EQU $04 ENABLE HLD & 10 MSEC DELAY (1=ACTIVE)`
54			`BBLEN EQU $08 BLOCK LENGTH (1=IBM FORMAT 128 - 1024 BYTES)`
55			`BMREC EQU $10 MULTIPLE RECORD (0=SINGLE, 1=MULTIPLE)`
56			`*`
57			`** TYPE III INSTRUCTIONS`
58			`*`
59			`IRDADD EQU $C4 READ ADDRESS`
60			`IRDTRK EQU $E4 READ TRACK`
61			`IWRTRK EQU $F4 WRITE TRACK`
62			`*`
63			`** BIT FIELD TYPE III (READ TRACK ONLY)`
64			`*`
65			`BSYNC EQU $01 SYNCRONIZE FLAG (0=SYNC TO AM)`
66			`*`
67			`** TYPE IV NSTRUCTION`
68			`*`
69			`IFINTR EQU $D0 FORCE INTERRUPT`
70			`*`
71			`** FORCED INTERRUPT BITS (TYPE IV INSTRUCTION)`
72			`*`
73			`FI0 EQU $01 NOT READY TO READY TRANSITION`
74			`FI1 EQU $02 READY TO NOT READY TRANSITION`
75			`FI2 EQU $04 INDEX PULSE`
76			`FI3 EQU $08 EVERY 10 MSEC`
77			`*`
78			`** DISK DRIVER PATCHES`
79			`*`
80			`ORG $DE00`
81			`*`
82			`** JUMP TABLE TO DISK DRIVERS`
83			`*`
84			`READ JMP READSC`
85			`WRITE JMP WRITSC`
86			`VERIFY JMP VERIF1`
87			`RESTOR JMP RESTR1`
88			`DRIVE JMP DRVSEL`
89			`DRVRDY JMP CHKDRV`
90			`QUICK JMP CHKDRV`
91			`COLDDR JMP INITDR`
92			`WARMDR JMP WARMD1`
93			`SEEK JMP SEEK1`
94			`*`
95			`** CURRNT DRIVE NUMBER ($DE1E)`
96			`*`
97			`CURDRV FCB $00`
98			`*`
99			`** HEAD POSITION TABLE ($DE1F)`
100			`*`
101			`TRKTBL FCB $00 DRIVE 0`
102			`FCB $00 DRIVE 1`
103			`FCB $00 DRIVE 2`
104			`FCB $00 DRIVE 3`
105			`*`
106			`** ??? ($DE23)`
107			`*`
108			`FCB 0`
109			`*`
110			`** DENSITY TABLE: ($DE24)`
111			`** HOLDS SECTORS/TRACK FOR DRIVE`
112			`** 5" SINGLE DENSITY => 10 SECTORS/TRACK`
113			`*`
114			`DNSTBL FCB 10,10,10,10 ALL MINIS`
115			`*`
116			`** DRIVE & DISK CHARACTERISTICS`
117			`*`
118			`* BITS 1,0 STEPPING RATES`
119			`* BIT 2 TRACKS/DISK (0=40 TRACK, 1=80 TRACK)`
120			`* BIT 3 TRACKS/DRIVE (0=40 TRACK, 1=80 TRACK)`
121			`*`
122			`BDVTPI EQU $08`
123			`BDKTPI EQU $04`
124			`DDCTBL EQU *`
125			`FCB BDVTPI+BDKTPI+SMR6`
126			`FCB BDVTPI+BDKTPI+SMR6`
127			`FCB SMR40`
128			`FCB SMR40`
129			`*`
130			`** DISK DRIVERS`
131			`*`
132			`* DRIVER INITIATION`
133			`*`
134			`INITDR LDX #CURDRV`
135			`LDB #5`
136			`INITD2 CLR ,X+`
137			`DECB`
138			`BNE INITD2`
139			`WARMD1 RTS`
140			`*`
141			`* READ ONE SECTOR`
142			`*`
143			`READSC BSR SEEK1`
144			`LDA #IREAD+BBLEN+BEHLD`
145			`READ2 ORCC #$10`
146			`* SEI DISABLE INTERRUPTS`
147			`STA CMDREG`
148			`LBSR DLY47`
149			`LDB #$00`
150			`RDLOOP LDA CMDREG`
151			`BITA #$02`
152			`BNE RDBYTE`
153			`BITA #$01`
154			`BNE RDLOOP`
155			`TFR A,B`
156			`BRA RDEXIT`
157			`*`
158			`RDBYTE LDA DATREG`
159			`STA ,X+`
160			`DECB`
161			`BNE RDLOOP`
162			`BSR WAIT`
163			`RDEXIT BITB #$1C`
164			`ANDCC #$EF`
165			`* CLI`
166			`RTS`
167			`*`
168			`** WAIT UNTIL CONTROLLER READY`
169			`*`
170			`WAIT LDB CMDREG`
171			`BITB #$01`
172			`BNE WAIT`
173			`RTS`
174			`*`
175			`** SEEK1 TRACK AND SECTOR`
176			`** ACCA = TRACK NUMBER`
177			`** ACCB = SECTOR NUMBER`
178			`*`
179			`SEEK1 STB SECREG SET SECTOR`
180			`CMPB #10 DOUBLE-SIDED ?`
181			`BHI SEEK2 DOUBLE SIDED, FLIP`
182			`LDB CURDRV BACK SIDE OF DISK ?`
183			`CMPB #1 DRIVE 2-3 BACK SIDE`
184			`BHI SEEK3`
185			`ANDB #$FF-SIDESL SELECT SIDE 0`
186			`BRA SEEK4`
187			`*`
188			`SEEK2 LDB CURDRV SELECT SIDE 1`
189			`SEEK3 ANDB #DRIVSL`
190			`ORB #SIDESL`
191			`SEEK4 STB DRVREG`
192			`*`
193			`CMPA TRKREG DIFFERENT TO LAST ?`
194			`BEQ FOUND`
195			`PSHS A SAVE TRACK NO. ON STACK`
196			`*`
197			`* IF 80 TRACK DRIVE, & 40 TRACK DISK, FIRST SEEK`
198			`* SHOULD NOT UPDATE TRACK REGISTER NOR VERIFY.`
199			`*`
200			`SUBA TRKREG CALC. DIFFERENCE`
201			`TFR A,B`
202			`PSHS Y`
203			`*`
204			`** GET STEPPING RATE FROM TABLE`
205			`*`
206			`LDY #DDCTBL`
207			`LDA CURDRV`
208			`ANDA #$01`
209			`LDA A,Y`
210			`PULS Y`
211			`*`
212			`** CHECK DRIVE AND DISK TYPE`
213			`*`
214			`BITA #BDVTPI DRIVE TRACK DENSITY = 48 TPI ?`
215			`BEQ SEEKVU YES, SKIP`
216			`BITA #BDKTPI DISK TRACK DENSITY = 96 TPI ?`
217			`BNE SEEKVU YES, SKIP (DRIVE & DISK MATCH)`
218			`*`
219			`** HERE IF 40TRACK DISK IN 80 TRACK DRIVE`
220			`** USE STEP INSTRUCTIONS TO PREVENT UPDATE OF TRACK REG.`
221			`*`
222			`ANDA #$03 LEAVE STEPPING RATE BITS`
223			`TSTB`
224			`BPL STEPIN`
225			`NEGB`
226			`ORA #ISTOUT`
227			`BRA STEPLP`
228			`STEPIN ORA #ISTIN`
229			`STEPLP PSHS B`
230			`BSR SEEK5`
231			`PULS B`
232			`DECB`
233			`BNE STEPLP`
234			`*`
235			`** SEEK TRACK WITH VERIFY & UPDATE`
236			`*`
237			`SEEKVU ANDA #$03 RETAIN STEPPING RATE`
238			`ORA #ISEEK+BHDLD ($18)`
239			`PULS B RESTORE DEST TRACK NO.`
240			`STB DATREG YES, SEEK1 NEW TRACK`
241			`LBSR DLY47`
242			`SEEK5 STA CMDREG`
243			`LBSR DLY47`
244			`BSR WAIT`
245			`BITB #$10 CHECK FOR SEEK1 ERROR`
246			`FOUND JMP DLY47`
247			`*`
248			`** WRITE SECTOR TO DISK`
249			`*`
250			`WRITSC BSR SEEK1`
251			`LDA #IWRITE+BBLEN+BEHLD ($AC)`
252			`WRITE2 ORCC #$10`
253			`* SEI`
254			`STA CMDREG`
255			`LBSR DLY47`
256			`LDB #$00`
257			`WRLOOP LDA CMDREG`
258			`BITA #$02`
259			`BNE WRBYTE`
260			`BITA #$01`
261			`BNE WRLOOP`
262			`TFR A,B`
263			`BRA WREXIT`
264			`*`
265			`WRBYTE LDA ,X+`
266			`STA DATREG`
267			`DECB`
268			`BNE WRLOOP`
269			`LBSR WAIT`
270			`WREXIT BITB #$5C`
271			`ANDCC #$EF`
272			`* CLI`
273			`RTS`
274			`*`
275			`** VERIFY SECTOR WRITTEN`
276			`*`
277			`VERIF1 LDA #IREAD+BBLEN+BEHLD ($8C)`
278			`VERIF2 ORCC #$10`
279			`* SEI`
280			`STA CMDREG`
281			`LBSR DLY47`
282			`LBSR WAIT`
283			`ANDCC #$EF`
284			`* CLI`
285			`BITB #$18`
286			`RTS`
287			`*`
288			`** SEEK TRACK ZERO`
289			`*`
290			`RESTR1 PSHS X`
291			`BSR DRVSEL`
292			`LDX #DDCTBL`
293			`LDA CURDRV`
294			`ANDA #1`
295			`LDA A,X`
296			`ANDA #$03`
297			`ORA #IREST+BHDLD`
298			`STA CMDREG`
299			`BSR DLY47`
300			`LBSR WAIT`
301			`BITB #$D8 CHECK FOR ERROR`
302			`PULS X,PC`
303			`*`
304			`** SELECT DRIVE`
305			`** IX -> FCB`
306			`** ACCA = NEW DRIVE NUMBER`
307			`*`
308			`* SAVE OLD TRACK NUMBER IN TABLE`
309			`* AND SET UP TRACK FOR NEW DRIVE`
310			`*`
311			`*`
312			`DRVSEL LDA 3,X`
313			`CMPA #3`
314			`BLS DRSEL1`
315			`LDB #$0F SET ERROR VALUE`
316			`* SEC`
317			`ORCC #$01`
318			`RTS`
319			`*`
320			`* SAVE TRACK POSITION OF PREVIOUS DRIVE`
321			`*`
322			`DRSEL1 BSR PNTDRV`
323			`LDB TRKREG`
324			`STB ,X`
325			`*`
326			`* SELECT NEW DRIVE`
327			`*`
328			`DRSEL3 STA CURDRV MAY BE 0 - 3`
329			`CMPA #1`
330			`BLS DRSEL4 ONE DIRECTORY ?`
331			`ANDA #DRIVSL ROUND OFF`
332			`ORA #SIDESL SELECT SIDE 1`
333			`DRSEL4 STA DRVREG`
334			`*`
335			`* RESTORE LAST TRACK POSITION FOR THIS DRIVE`
336			`*`
337			`BSR PNTDRV`
338			`LDA ,X`
339			`STA TRKREG`
340			`BSR DLY47`
341			`BRA OK`
342			`*`
343			`** CHECK IF DRIVE READY`
344			`*`
345			`CHKDRV LDA 3,X`
346			`CMPA #3`
347			`BLS OK`
348			`LDB #$80`
349			`* SEC`
350			`ORCC #$01`
351			`RTS`
352
353			`OK CLRB`
354			`* CLC`
355			`ANDCC #$FE`
356			`RTS`
357			`*`
358			`* POINT TO TRACK TABLE ENTRY FOR THIS DRIVE`
359			`*`
360			`PNTDRV LDX #TRKTBL`
361			`LDB CURDRV`
362			`ANDB #DRIVSL`
363			`ABX`
364			`RTS`
365			`*`
366			`** DELAY ROUTINE`
367			`*`
368			`DLY47 LBSR DLY19`
369			`DLY19 LBSR DLY5US`
370			`DLY5US RTS`
371			`END`
372

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