Moog Song Producer, Руководство по обслуживанию

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The drum output circuit consists of
latches U12 and U13 , buffers U6 and U16 .
pulse t i me r U1 4 A and R50 and d r um mode
latches U15B. Th e drum outp u t latches can
operate in eit h er a pulse mode or a latch
mode depending on the status of flip flop
U15B. I n the latch m ode . t h e output of
U15B i s " 0 ", disab l ing reset circuit U1 4 B.
Data f r om the buffered data bus is latched
by U13 and U12 D O
=
DR UM TRIGGER 1. D7
=
DRU M T R IGGER 8 .
The output s f rom U 13 and U12 are buffered
by U6 and U16 and sent to t h e Drum Trigger
outputs 1 through 8 . W hen Pin 13 of UlsB
is high. the drum output operates i n a
pulse mode . W hene v er a "1" is w ritten to
a n y output of U13 o r U12 , d iodes CRS
through CR12 coup l e t hat "1 " to the input
of U1 4 A. U14 A charges C26 through RSO .
When the v oltage on C26 equals 2.5 v olts,
the output of U1 4 B goes negative resetting
latc h es U12 and U 13 bac k to z e ro . C26 and
R50 . a drum pulse w i d t h tri m, sets the
time constant and t hereb y adjusts the
pulse w idt h .
The CLO CK I N (CI) and CLOCK IN DISABLE
(CID) circuits consist o f U1 , U3A . U2A,
UIO and USB. T he C I and CID circ u its allo w
e x ter n al inst rum ents , such as drum
machi n es . to be used as a time base for
the So n g Producer . When enabled, clock
pu l ses on CI generate a non-maskable
i n terrupt that is fed back to the
Commodore 6 4 an d used as a timing signal.
The CID . . in conju n c t ion w ith latch USB.
can be used t o in h ibit the actio n of CI .
Either a " 1" o n U SB or a "0" on CID will
i nh i bit U2A from pas s i n g the clock signal
to UIOD , thereb y disabling it. If U2A
gene r ates a n i n ter r upt , the signal is
i nver t ed b y U I OD and aga i n b y U10C and
se n t t o the NMI l i n e. Since i t is
impe ra ti v e th a t n o n - m as k a b le interrupts do
no t occur unti l the sof tw are sets the
Commodore u p to re c ei v e them, the A
sectio n of U S is used to i nhibit the
interrupt s u pon po w er up . This is
d escr i bed ful l y in th e IN TER R UPT DISABLE
section .
U4 p r o v i d es both a CL O C K O UT (CO) an d
CLO C K O UT D I S A B LE (COD ) fo r d r iving
e x te rnal d rum m ac hin es. Wh e n e v er a "1" is
wr itten t o B DI of U 4 A , U4A c h arges C9
throug h R 16 a n d R 17 . Wh e n t h e v o l tage on
C9 e x ceeds th e thr es ho l d v o l tage on the
reset i n put , U4 A r e sets t o "0" producing a
p u l se. R16 . R17 a n d C9 se t t he pulse w idth
to 665 m icrose con d s . Thi s is bu ffered b y
U6B an d fe d t o C O. T h e C O D is latc h ed b y
U4 B fro m BDO.
U 7 is a t r i -s t a t e bu ff er u se d
F oot swi tc h I N 1 a nd 2 t o t h e
W he n e v e r me mo r y l o cati o n D EOC
rea d . th e data on Foo t s w itch I N
tra n sfe r re d t o th e d at a bu s on
6. "0 " = s w itc h d epres s e d. Al l
bi t s ar e u n u se d an d se t
resistors R3 0 t h r oug h R3 7 .
to feed
da t a bus .
(5 68 44 ) i s
1 a nd 2 is
b i t s 7 a n d
othe r d ata
to " 1 " b y
To r eceive in f o r mat i on. t h e se ri al d at a
stream is fed to M IDI IN t h ro u gh J 2 0 . I t
is opt i ca l ly isolated by U2 2 an d fed
t h rough buf f er U21D to t h e recei v e da t a
i n put o n U 1 7 . W he n the recei v e d a ta buf f er
rece i ves al l 8 da t a bits. a n i nte r rupt
request is generated wh ich is fe d t o the
computer through UIO and a "1" i s set in
bit 7 of it ' s o w n status register . The
Commodore 64 reads the status register of
each A CIA and when it fin d s a "1 " i n bit 7
of th~ status data registe r, it th e n reads
the rece iv e data. Then it is r eady to
recei v e t h e ne x t se r ial data tr a n sm i ssio n.
The recei v e data stream i s also fed t o U21
and out the M IDI TH R OUGH jac k to dr i ve
ot h er MIDI based instrume n t s .
S i nce U17 through U20 all t ransmit in the
same fash i on . w e'll only loo k at U 1 7 .
Whene v er the computer w ants to se n d a M IDI
command . it first w rites into the transmit
data register of U17 . When the data word
is latched. U1 7 adds 1 start bit , then
feeds the data out in a serial stream to
output "W " . A t the end of the 8 data bits.
it adds one stop bit . W hen the w ord is
successfu ly t r ansmitted, U17 ge n erates an
interrupt . telling the microprocessor that
it is ready to r eceive the next word for
transmission . U18, U 1 9 and U20 operate i n
e x actly the same matter as U 17 .
It i s i mpe r ati v e t h at no interrupts ,
either inter r upt requests or non-maskable
interrupts are generated by the Song
Producer before the sof t ware has
programmed the Commodore 6 4 to handle
them . Therefore , USA i s conf i gured to
disable both t he NM I v ia UI OC and IRQ v ia
UIOB from t h e Song Producer upo n power u p.
W hen po w er i s s u pplied t o the Song
Producer , C l 8 hold s t he reset pin of USA
high fo r appro x imate l y 1 seco n d. This
causes t h e "Q" outpu t t o go lo w , disabl i ng
U I O w hich disables both inter r upt lines .
T o enable bot h. a "1 " is w ritten to USA
w hich enables U I OB and C. Therefo r e , the
clock i nput can then generate a
N O N -MASKABLE I N TERRUPT (N M I) or the ACI A' s
can generate an INTERRUPT REQUEST (IRQ ) .
M IDI stands for Mu sical Ins t r u me n t Digital
Interface. M IDI is a d igital serial
communicaion c h annel (sim i lar to RS2 3 2)
that allo w s similar l y equipped inst r uments
to communicate w ith eac h othe r at th e
lo we st le v e l the y b oth u n d e r sta n d . In t he
case of the So n g Pro du cer , M I D I allo w s t h e
C o m m odore 6 4 to commun i cate and co n trol
s y nthes iz e rs and d ru m mac h ines . It
communic a te s w ith 1 0 bit w ords co nsi sting
of one star t bi t , 8 data bits a nd 1 s top
bit at a 31.25 k Hz b it rate . T o re d uce
ground l oops , th e M I D I i nput i s opt i cal ly
isolate d.
T h e M I D I serial d at a s tr eam i s b oth
transmitted a n d r e cei v ed b y a s y nchronous
com m un i cat i o n i n terface adaptors ( ACIA )
U1 7 t hr ough U20 . T he A CI A' s are
prog r am m able de vi ces wh ic h can selec t
d iff eren t d a t a rat e s , w ord siz es a n d ot her
p a r ame t e r s . Th e sy s t e m cloc k 02 i s d iv ided
b y U15A to 500 kHz. E ach of t h e A CI A ' s is
p r ogramme d t o d i v ide this c l oc k by 1 6 to
g e nerate t he 3 1. 25 kH z ti mi ng s i g n a l s u s~d
for M IDI tr an s mi ssi on o r rec e p tion .
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