[comp.sys.atari.st] Hardware: Read IBM disks with ST

mdoerr@incas.UUCP (10/08/87)

This posting is in response to the ever increasing number of people who
want to hook a 80-track 5.25" drive to their ST, but want to read 40-track
IBM-PC diskettes as well. Once upon a time (in 1986) the german magazine
c't published a solution called the step doubler. I recently build that
circuit and am now happily reading and writing 360K MSDOS diskettes
as well as making backups of my hard disk to cheap 5.25" diskettes holding
800K of data each. Below you'll find an UUENCODEed and ARCed Degas Elite
PI3-picture showing that circuit.
*** No warranty implied: If you fry your ST or drive you're on your own. ***
Note 1: Most 5.25" drives do step flawlessly at 3 ms but won't be able to
do 2 steps in 3 ms. That's why one should lengthen the step time of the
switched 5.25" drive to 6 ms. This is done by changing some low memory
variables, which should be mentioned in the Abacus books. I remember that
these addresses even drifted along USENET a long time ago. I actually don't
need to do that, because my Philips X3134 is capable of doing 2 steps in 3 ms!
Note 2: While having a hot soldering iron you should add some open collector
TTL drivers (a 7407 is fine) to the following 3 signal lines:
	Pin 2: Side select
	Pin 5: Drive 0 select
	Pin 6: Drive 1 select
These lines are driven by unbuffered outputs of the Yamaha sound chip that
isn't capable of driving heavy loads and may easily be damaged. All other
outgoing lines on the floppy port are sufficiently buffered.

Have fun, Michael.

/|\     /|\     /|\     /|\     /|\     /|\     /|\     /|\     /|\     /|\
Michael Doerr, Uni. of Kaiserlautern, Germany --- uunet!unido!uklirb!mdoerr
/|\     /|\     /|\     /|\     /|\     /|\     /|\     /|\     /|\     /|\

table
 !"#$%&'()*+,-./0123456789:;<=>?
@ABCDEFGHIJKLMNOPQRSTUVWXYZ[\]^_
begin 644 40_80_tr.arc
M&@@T,%\X,%]44BY023, !!<  $8/$:Y@V$)]   ,  0<N , TK0!#P(\>@#@a
M R   &  R/ 0  8 #@H2&)#IH<,''SI>!#"@HD1()P9\"/3I$R"'$"52A'C1a
M@8&" PYT;/CRDTB(!TP6/'$@0Z!,'6]"&B"SXD4#2@=$O9@!$\6144\2S3 Ha
M0](/#Q[,F+CIP2.P!CZ<!6 @PR>+$ZT"PO @@Z$89V<PA&2B[J"ZGPRI_71Ca
MXJ^6:@6W?)G)Y0>2'ZX^:!RKY2V8D$H\V&!H<V"CF'P8QH3!J*&V'4.F!J12a
M9(#&M9#ZFIEY0P=#&3H!,D 7$X^)M3B5?G2Z*EOC 78GMSC94(U,OFF7V)"!a
MD=?=&#Z$!OZH=."TF(Z'3VY@>?9,AGY\"HVY1$CK24MCL@%\D%7TO)\B-\3 a
MO-?TI-EP$5\AW8==56-E$$L@]YV&@7[AV<7 3*6AMP-I,PQH@DJ8?. 2;Q[.a
M\E)E/GWRR 'KL:5=0XIYU-)=Z\W@4D$E($070[R9%0L@#\3PR62//#+ (^$9a
M\$!X#Z3U"$1J$0<"D7@]!,D_!5$)"100%/3$24]D"4F76GJIR62>0,1'04I@a
MT,$F$ F"YGD/N0G)!C@4Y,(&/CTTR#^0M%!0!QELLI.<=!8$00!_>L4F (1Za
M>>B?9)I9T :.(@J)#Y46A*FAEFX*R:.79AHJIYJ*ZBFHIUHJ AZ3BBH" :V2a
M"HD(=<[I*A"Q?JKJF;;*FFI!'H3T$*^4RMH!;S,U:FQ:R1:$0*T#<%"0 UF6a
M5% #EB*0$204K+33GI#L(*5-K\7I++320D(M25)BZ^RV!8S;UI*,.NOE  A,a
MFZ6E#F0+*R3Q%A3630#PBL"]^:J[[[3^%A0P)!P@K"\ _#8,L)01XY3PNA4[a
M^^_#&2^U\<+J6@RRQ I3S+#'#F.,,L<K0X+ QRYK/''',M-<4,CXWASSS"WOa
M_#+)_;)\<4$3L"JS/S:GC#,"/TB9$SQ(_XN G#T[_3,(4A/@Y02U7MTTS"4[a
MRS5.7E?M+-8CJURVS&<OE38D2:\]-M'9QCW W!RP[?/;".@]=Y(X&>RWUH +a
M[N4"2AT@9P$'> *$FP_P20(^.(T "0!G$R#'W H\8.)C#CQ6+R0&!(&$F_FVa
MW3$ "0] AC1G,Z )$5XJ@ %JN\T$+@'P#. ('*S#_G?1QB]5 A>=KT)([DD*a
MVY:YD'CM]>K&N[YR\@.8($7GRN!>D (!&%):[]1[?< W1!2O?=G<CQ!)YW*0a
MD/L'0SY6U[ :W>O^\8A*7@$4=ZT!*<!_V0,@1!(VP*YY"0,(;)T"!4A 2$ 0a
M)_]#'/(86,$++B6#9-N@PSH8P>2%,( <=&!!/#@ IDE0@RAT6-1P<@"J6?!>a
M67KA"1?H,)W=$"<Y-"'>> @P'TY@0',;0!#?)\(B!HUN*.@?$!,(0R(6P(A(a
MD.)2E@B RD$B 1596 #XE "JJ4R 1N15$KF8,#!"1(P%24"6SLA (R9LC0ELa
M8QA59BDY0B2&3CS:#[>8QSCN$5%]G",@K_C$":@1AX7\XB'=YD<Z]O")C'/8a
M3>2$1PGJ\8U\C*,BK>C#T(VNBVX!!"<AZ4E#@A*1HOPC*9^H.][]!P![^@<Pa
M ,!**KJ1EZ'\XBC12,OH=>26;@( KGKYPE_"49BR)*8@R6<^BB 3(LN<HB>Ea
M5!X>3#( 81MF'6F)O[6$91" .),R@4E(";H1=0,0P#>)8*]HCE.0#1@0 K+9a
MSNQQ,P <^.9O9";.2PK2 OQ48A[_*<]74LQJ!0WDPQ * &C525JM^Z<W'0K.a
M>EI2HE*BZ _(B+DO\JF-'_@'/!;I0XI:%  839XS@UE)ECZ1HEXZ0#,YP=$Xa
M3N A-CTH/W4J4U'T](L4P%50)SK49AH5F+!$JE)G*<BZK3.G3CUJ I+Z4496a
M%5=7+0A1V\A3J%+RIUTU(JO""HFQQM$06H7 +I<JI0G BJUNE61<[6G0AUFUa
MJ3+]9BS3>E/ ?M*LB>0K2)&F3L.Z$K&#I2O2DNE8O4(6FH2M*F79F=>91K6Fa
M/#S)WM:Y%"DM(*5M_9T-.RM8S,9P"N" "*R>41'3YG2S7VQF:T%K/$F,!%9(a
M  -$;"M6W"9 @@,( #B",0XS"I8Y1H))0?5!,.".A+AM;6P<\[4 8 Q@ #$8a
M!@R$"X!O1@ 8I7$$5T!I20D$$+AWQ:X"<)5;V('@NP  !@QV65Z.R@ ,#RH/a
M7(%I20'T-R,(,'!_(;& W-'WN !(@'>5"PPPD/>;$@ %70R 7P('L'),0V?Ea
M\"$ #RRXP>-[<+X40)*( $._P^7H!$" @?*5YR&CK)Z!Z8G@ "!*O@^6U@+ a
M\5T8!&,0$NDO,$L2@/.6AC\SR3$!#'P"0, J7XXXL8/CF%+,#2 >XYA'/&(+a
M %^ <@#_H%)#SF(BB%Q@KAHQ, F <&4 !$++*8YC3"U;+4 DUFU3!L (K&R\a
M,@%YNS(MZS,3@%9+!1H.&(%= ( QZ8*@&!+S170;G[IHKCK:P'_XAPO'J$M+a
MY[1.I(7PIH^*@!-08JHZ!@"D>TSI73(XIV!5<5%9#08JP#K0( ! G1^"W0.La
M5==D9?4()@'4.'-.V,8CMJG%2L]4-W/ ST2 _> <ZV /&\]M136R'YOM$T!#a
MEK'&U94#>.CZMC'-@%@T:@_ M(<<X!\DCO&MQ:K=^G;76=^$@)0.(&4#2RW!a
M^KZTX["IZ6#+[)LQ&+B4Y6&I[R(COM-NJW'S)6& <U3@8I6R()1" !1<=]KWa
M!E@N;:UJAR,@X!)'-P'D$;L ("/8>/Z8G!@@9%N__,Q^!GE;I;P &\;S ?PEa
MKLX+PH NDYLD:8ZL1FRXD=B6=MH?XQ7/ POT/_-+Z061@&[WZC8'@!T28N?Za
M94&KKK.G_;"+SK'9I[VMMS_]LW(G;MW'OO:\TSWL?(\[NN>^[W_9'6!E"@$@a
M6@NY78+#[X4'?/(($(#- 4 ,BS^J 8" J!SG2"T:(2X#M?[" I2)!)F_K '\a
M_'AT(ZLK4A.]01E0^CN? !B,1R0$/!]@VEAKWUXJ0,)H+\ R<2WW$&F]VW*$a
MD-!/._A>(C[<:<K[ !PE]M-V> &BGR\O>I9B9#2CI9"%%.SOV^%I;VN^#%P]a
MDAT@@/1-;D&4%!;G[YN^!2"]6-<O14N]G^%+\773AG\[ES!$Q7YIXW_PAQ,"a
M>&LE42L$4(#[%Q#])U8+&(#38EHI!0@C53TKAVCJ1X'MYS;_1UKRUW9,]X :a
ML7$3B(#N=X$G2'@3P((AZ((D"(,-2#[A0&9A0&;]!F$U6(%MA8,9.#X#, -)a
M-@XG40"ZUE;28H,*"( Q*"4*<(20%@#C &D TX0%,%+\((():(%2F(-8" LDa
M,09FN(4@.$ P!88O.(9%B&E'*!$#, ]+R(7!QG\C&(4FF(-S"!%C<(=KB#EZa
M&(9#"(<HB&D!L(,0T8,.PX6$Z(8WB(B$1U'U!3"0A@ 1 (46*  @$'\-:(E a
MR(::R(E#Z(F@&(>BB  @!@"A!@^E*(0$,%+X$ "HR("JJ&+\MTRQN(<:D8>Va
M^(FXF(BKN(N\Q $1< "RF(<#( @@8'536!"B^ !>5FHI%0]\4@!4,T;5$UL@a
MUH$%D(OC8XP0@(S*R&#,Z(Q6)P$A15\*0(X $ %,EX<!X7!H!0F6&#JBYHHJa
M%8],1XOUB#3M&';R^"F>*)#22%\24) 0<)!T,Y"0@ ,0*9$)61 4B8_NB"*Xa
MP@/RT$4\H(4-]@#!]I$(B9&6ICH!(0BX(@B;8&L*(!&DP#F#8&OL6)%R* B0a
MQ@'S  @'P &JX' '= !UPI'H!Y$*0  $D$4@,%^!HPQ "0'(0 (!H0A%:9,*a
M< #$0$\^( \@\ "^( =/^0Q&Q0-@&783>98V>9&6J);TQ986B98F&9%PN98Aa
M%6IR625X.25Y^0$C05[I,@#"-2!2T9=PL13")5Q+P1OSQP<CP0._X0 #-0!:a
M2  <8 :(20&_ 0#D)5J(.0!/@1/D19B=V3AF@!-F4)J5.1(0*!&!&79FP Z:a
MR0-FP ?&P -\4)HXX -^   ^@ ._ 08\@ -^8)M\0)P0T9N_80:V"0!F@ -Ga
M8@!N8!%@,)R,"0"UZ0-GP@=\L)L X >EJ2YFP#1@8 !F  /&<)IL()T78088a
M4)I@P)[MF9BG"1'L69IFL!0%TYX P !V8!$\T)[L:9VG"0/WZ9D0P0#?Z0!^a
M8 V:Z0/E:0U^  :L@@'_R9P8L)O3^2 1:@8.6IH6NIL%JIGZ.:*\X9T7 :'Ea
M>9H 1A,):@;&H)D#R@<6EIZ[LYX8<)@ =J/O63T2P9[")9ONJ9\$"E,^VIP%a
M P8^0*"6B0$2,:3@^:)^X -)R@8\\)X 8)L9X0..V9V."9E@P <=*A%:^AL4a
MZIZRR:48P0.0R0>01J4&  ,."@8.(!%16A L<)F(20"\4@"(J691@9@)H#0#a
MD)R:6:B">9@XH10&$)H0$16125YU,B 1\*?ZE)Y+$:"%RJB9FJCSUYF?>:F$a
M69@&"@D/X*#%N9VG>JKTR0.B,9U7:J;"29S&R9NL6C".>2;L()RT>B;3Z9C*a
MR9C!J9L#Y0 %^I[Q23!FL*A7VIY@D)[&&I]2,9_,J:PJ6IK^\"#,B9__:9ELa
M<)KM>:/Z"9Z6::S3>9K>29]:RA;,RBH9>J'OV:'HFIR669K6@*UF$*'J&J%Xa
M$*$72J$7.BTJ2J[O.:\7T:TW49_-JIDY:F'W20 ]FJS,.:_6::\69J$S:F'@a
MRAN(Z0!2"IQFX  >JYP!B@?8>:4<>Z;#J:95"J8#RILEJYQG6IM96J4FZZM5a
MR@-+P0>061#CE9<A0%Y3X3"?"1?Y"1&["2\7,9E JQ%X@$0D1Z9AM[0 ,R %a
M$+3?.0 ,T(94"X%22P"66K4:X:$#0JS$.9M:>B:YR9W&X)RBD:L@ZIQP@0'"a
MBK;5^:NW":;+R9R^>:5X6YRQ&:O7<I\)H)X080P "@#7>A&,69I9"Z[S^:W9a
M.K@66IKD"3"O^B#?V0#WNJ,$<*[^"A'U:J7U>A$ 1KG^>:&E";F;V[#G^J&\a
M::ZN:@!^H*'74J6<:Z4U*A&,::6&2[KZB9H:F[I&:KL-:ZP P 8WFJV B9]+a
MFKR0D$\KZZ!:6II8*A%4BJ36J::Q2;T8H;/+*9N01J%?*KVR>1%XL*7D"YQ7a
MNA0["PD:@*=[.;0C49W[&6DRH[2-JA&[N108:ID:$17[2P X(+:&*C!6BQ/2a
M(BU4BP%<F[_5\Z>;^L"<6CU4RZ@,MK9@"@!NJ[=G0J9S^ZJSRYQEV[<'.IN:a
MJ9T%8[:[NI^G:9L4*J6YJ9RZ>L&'F[CY69HT6KKV"9^1RZ*E>9LB6SW*:Q$-a
MNSL8:P;=BJT,%KKTBJVEVYVG>Z[>NIX;6CVM2Z X>I\'BZ]*RJ]CVI[[JL0+a
ML+NEV;LBRK@P%;P1R\!7RK#58[SOF<4 (QKC"J.VVYY0(;=LD*.6=KVB(;/;a
M6[\.X+T=[ ,.$+[1RZ'EVYT^(%P;*IL.>A-:ZL@^(+ZLJIT\0)Y="BR(R0&\a
M\@"\HF8X "WT6Q,.B@>01K1*D0!149WL>Q%^X >0!L!A@Y@2@ 'XR9PX<5%@a
M8 =L "V?RLJFJ1$<4"<,P !U0JE""Q&("0%:JJ')";<7<:,FJL&Z>K;,V;>La
MNIS-F<'8BLL#0*NM2J':R:$I^ZNB\;S&>JDW'+=N4,TV'*+W6;4ANKB!>:''a
MO)[^N[AOS*S=ZK_/6[[\>\9Q:P9N$*"CRYQ2S+](>J]!JIP6\12*>:^_&9\$a
M\)_Z&J$#U0#D"<Z'.:)$BL1U8L82>YJ-/+!66KHWP0'Z7">6>1.ENQ0^H+'-a
M:F%*T0#%R;Z_B;(8<<J0!LC3^[H&4*52>J8>>R8*>J4DB<W 29P&X+VRN;(%a
MH0*\\KY?FI<)(+5001,%(01:33 #\@-V:[;+69M]&]:"*Z!36Q!B7<6=2Z\;a
M6LV0\ /$^\8_S+!6"@E (+XL&]1^O,AZ&=A68B5<@%HZ4! 5X"4Y8"F)71"+a
MS72(>3".;2D,D*?8RDZ/#0F5'=7W.A**3=GC6:"""0%TIDRP4MJH?=JJ;=JLa
MG=JMO=JN'=NP$@20[:!+<=F?#=D<.L6@! F9S0!1.M2&/$6^S2^\8@"Y#0F-a
M7=R('7PI51 4P(U9"PD1P-C09RG1[3"64@"64MW-[3"@DMT L]W=;=W@C=WDa
MK=T%X=W*'7R;@]X $#EU$D!X$%OE_=W54WD $ [0'0 9$01-  [A\-]!P=_4a
M;=VIO3GA -L,_MH $ 0., #.4 40,.  D ?D  0+[N"R_>#X70 *WM\.X#5Ea
M4.$940!)9>#LO=P@[C;9O3XY\"@ @ <9?M_M?=[]K=[CO=[F#3#AG=X[?N ?a
M_N,ZSMT\_N'/#7YM94,)(-U'?N,^'D#^YR4GT./;)^4A-Q16+N-3KN7X30 'a
M\-[H-@": Q'L5.4?#@7\33$9 0"S@Q%4CN"G'>;[/=L9 03+ P34TN%\WN!]a
M[N%0CI05_D=M[CUP[N6!?@#0@.5+(3^]C>90?N7H1G"(SN)<GN4HL>6,3NE?a
MY.1"'NE)SHTU%$>6L@"(\MRHQ6)N8^F;[B5-;FF=UWFDCFZL/NFN7NJQSDZOa
MONK7;>NSSF"Y?NNT[B5@+N9N0^:6I^NXSDNRWNG#[C!J3N@0\>;KTND9 0[7a
MGNW[S4O\#0'8#@#?_NUK+N?*1.<;#N'*E.=[WN#H'N[:ON 5[C7N#NX9<>YIa
M/NZ%+@6';NWTWN_BSNV\-.__SNL:0>>,3N:1T-NO#NS,KNS/'N6^[NP,_RC"a
M3O 03X+"/O'-ONN:'O$+;^H-7_%6'NI\,NI*KHW+3O&S;O&2CO$0 2^@ O(Ja
M[^PL?^E#%Q,X/O%QX/ UW^H086N2/O%W)O)#CN6P0^<.A3HQWWE#O_(]3GDAa
MSN9PH>_KPGX%0"TIW_0T3^Y 8  *;N< @ 0'P EZ3MJP32U!0 P</MM>$P^4a
MV>%!,-M?3@!1[]^P0P82<.@,A/5 F>MYO_5?KNA&CP!G$ V@Y"7('0"YTWG\a
M79 <_^'&WN4.E_@)0S[QF/!"AP",7NLN/_F'DB\-@0&#( QY0&:($@%1P$L/a
M\0",$ 3O("UGU/$N3U^)?U<!@ *$8 !IHS(1$ .\!%:4( 0 \%2;[]QJ)NI4a
M0_N'<E<"@ 2#( @X8/H 3]H40P)!< RP7_PX[O+<M/RRQ0> ( 1 ,$H4CRL"a
MX -   +$__ MW^7='P"@3P (< ^"T ?2/^@@)P $L ?/D/WL;_.4_OZ5?_J8a
M+R6:__#%'OM_= [GUO 4<P[)?BB+'X^I[_C:7SU>@^]O1/6'TN84D/?,WO?Qa
MZ/M___CMC=KF#O9 0 YDC_9W?@YD[S5IO_8/[C4+S@%P+_>1'NU2[V-YC_49a
M@2CZWO :S_-/;_#1% #Q((\-3S'WD/ -K_$\+_ON/W]+'X_QP/.R[_[SM_2\a
MI/6/'^DV3^GO#^LA[_1(?OPEG_SSM_0A[_1%[^O*G_(;K_T7+_GSM_0A[_1%a
M[^N>G_(;K_W5,P"1_T?GD.Q9@OA+'_)./_>#+O6\1/5!!#!8K^WSWNW=+O#Ua
M/NRH;>Y@#P3G0/;KWMIHK^WS#N_P+O#U+O>!3@#1+O4!0 !Y7_4.@_7:/N_=a
MWNT"7^\/OQ&1_T?W8/AFI?0IO_':?_%=GE\Y+_,;K_T7W^41D?,RO_':?_%=a
M;K]!+_,;K_T 0_)+_D?9N%)\DK6HSB>JWO&0( ,=#PDRT/&0( -/+_@%(0-6a
M'NV0( -<3_=UOO9KO_9KO_:L3=N!KO@&+@-/K_B6(@,=#PDRT/&0( ,=#PDRa
M,/)6(@,]GMG+G=G+G=G+G=G+G=F)_>=__N=_#O?XG=G+G=G+G=G+G=G+G=D5a
<8-AY:24[@"@&%LX8:&#A#$NP]!!4   J !$: /?Xa
 a
end