RSC Forth - TIMARA
Contents
1. S32104 49410 Wouy FE pon ndu uoj3einpoj aun indu uo ie npoy o 2 143Z SIYIU S PI4qAH 243 40 23 04 e 2a71 u311v aug jO ue42e g 42019 e 32104 f Junot baJj 391113 v a Es 8 Asoway S4ayeads 3nd ng o AD 2 WAS AS a Y Asouayy 92 OA J3YIO 03 A AS AS Q 9 V E E ES Jeuap wouy z Bus S7AICRO V7ERRUPTS NA AYBRID 23 2923 A D ay 82 203 PUISE DE 6 10 150 PULSE DETECT ISE SC 15 A3 ez SL 15 BA I50 PULSE GEN 2 a DEV 47 P yon 63 e 42 ki B34 de 63 5 amp Bas 2 p 22 es io W Ss c V 829 D I NEN MP 63 7 N B28 2 g 9 N 3 x Y Bla E DATA z e Q By 15 m t le gt 8 0 Z f 61 1 ty Y bis 89 a a 62 32 a 83 LA DATA 72 2 fre 87 2 64 44 61 Aan BL RER 63 4 63 5 es w 62 63 7 B40 id B43 BI BA 8 5 B19 35 MIO MIDI IN RS232 1200 300 BAUD K LIM 3 10 R 22 2 d 2N2322 m ZN 10 a 9 L Q 2 770 EN IDA D ste TE 798 Ai 13 Lei A IDA w LE u av D o D Ow 7 CN AMAZ Y SN RS L w D B d S SS n 9 A o L A XZ XZ L o 3 Y YU 9 2 Da MD OUT R w Ag u Ag fa y 8 0 MY LA pi gt 272312 SE TB jij di 7 NAT ICs 129 790P I 7404 36 AER Cox ERROS R3 29h Rar LIARA NT RANI L Oe Z Eti A De Ap SA EPROAAZ DEV 12075 60 IEF 8D0 ben 450 J2. 2 BSWRP INPUT DEPTH x n DO y Shifts the 16 bit number x leftward by n bits and leaves the shifted result y on the stack Operation is the same as y x 2 XN y Shifts the 16 bit number x rightward by n bits and leaves the shifted result y on the stack Operation Is the same as y x 2 x y Performs the operation y 2x Same as 1 LSHIFT x y Swaps the two 8 bit bytes in the 16 bit number x on the stack Used in a word to stop execution and wait for input from the user Execution of current word is halted and all words and or numbers entered by the user up to a Return will be interpreted and executed after which execution of current word continues Example HXCONVERT Please enter Number INPUT hex equivalent HEX DECIMAL n Leaves the number of 16 bit numbers in the Data Stack before DEPTH was executed DATA STRUCTURES TO PARAMETER PARAMETERS HYPARAMETERS EXPARAMETERS Used to load data Into the data structures described below Format used is the following n TO X Used to create a single data variable N PARAMETER H Creates a variable named X with an initial value of n n TO X Will update parameter X s value to equal n X Executing the parameter leaves its value on the stack Used to create a set or vector of data parameters grouped under one name 0 PARAMETERS X Creates the vector X containing n data values ni TOnX Stores the val
3. RSC Forth THE RCS FORTH MICROCOMPUTER FORTH LANGUAGE Of all the computer languages you might be familiar with Basic APL C Pascal Fortran Forth is probably not one of them There are however some very good reasons for choosing Forth For one thing the language is compact it is able to fit in a small micro system such as the one you will be using here Like Basic It is an interpretive language that is you can execute programs immediately without waiting to compile them first as done in C or Pascal Unlike Basic it is last Forth was designed to operate real time systems and you will take advantage of its speed when you program the micro to execute musical events in real time For those programs which turn out to be not quite fast enough Forth allows us to streamline parts of the program in assembly language The RSC Forth micro includes a 6502 Assembler for this purpose Another reason for using this language is its extensibility The Forth language is made up of a collection of subroutines or small programs called words which are collected into a dictionary The programmer builds their own applications by creating new words to be placed in the dictionary The words are created by combining previously defined words Each word in the dictionary may be either executed or used in creating new words A set of words for using the devices built into this micro system have already been created and added to the dictionary In fact
4. FIFO first In first out buffer which lives In RAN memory at locations 1000 to IFFF hexadecimal It Is then up to the user to pick up the data bytes from the FIFO When not used for Midi Input the FIFO Is free for general use M filters out any FE data bytes and Includes FIFO wraparound ENB MIDIN Enables Midi Input Interrupts DIS_MIDIN Disables Midi Input Interrupts POP gt addr A variable containing the address of the FIFO output pointer PUSH gt addr A variable containing the address of the FIFO input pointer STAT gt addr A variable containing the address of the FIFO status STAT gt Is zero when the FIFO Is empty and is 1 when there is something in the FIFO FCLR Clears the FIFO POP n Pops the top value n off the FIFO and leaves it on the data stack PUSH n Pushes the value n onto the FIFO MIDIN An example of how to use the Midi In FIFO Waits for Midi Input and then prints it out on the terminal See source code 14 TIMER WORDS TEMPO TIME TM DUR DELAY TEMPO WAIT MS PARAMETER variable holding the number of milliseconds per beat To load execute the following n TO TEMPO PARAMETER variable holding the time position within a temporal piece i e the number of beats into the piece n Loads n into the TIME parameter Same as n TO TIME n Adds n to the value stored in the TIME parameter n Simple loopin
5. dynamically panned to any location in a quadraphonic space The two ramp modules X and V control this function The X Location module controls right left signal placement and the Y Location module controls front back placement depending of course on how the Hybrid s 4 outputs are connected to the speaker system and in what direction the listener is facing To localize in the center of the space send endpoint values of 7 to both the X and Y modules To send the voice signal to only one of the four speakers in the room send one of the following endpoint values X Y 0 0 0 15 15 0 or 15 15 To dynamically move the sound around the space use slow ramping speeds MODULATION PATCHING The Hybrid Synthesizer has two different modulation capabilities Frequency Modulation and Waveform Mix Modulation Any voice or voices can be patched to modulate any other voice or voices When an FM modulation patch is made the voices Transposition parameter becomes a Modulation Depth control When a Waveshape Mix Modulation patch is made the voice s Mixer parameter becomes a Modulation Depth control Both depth controls are ramping controls PROGRAMABLE TIMERS T The Hybrid contains four 16 bit timers to aid the computer in timing sound events Each timer can be programmed for delays ranging from 10 milliseconds to 15 minutes in 10 millisecond increments To use the timers you first load the timer module with a time delay value and then use the Hy
6. hardware counter TEMPO is a parameter variable which holds the duration in milliseconds of the smallest time division in a piece We ll call this a beat TEMPO is a word which will load the counter with the beat duration stored in TEMPO and start the counter decrementing WAIT is a loop program which waits for the counter to reach zero Use the above T word instead of WAIT if you need to use the micro for other things while waiting MS is similar to DELA Y It waits for n milliseconds before executing the next word The word KK was created to perform the same function as the short two line program at the start of this appendix except that it takes advantage of the hardware counter and its associated words KK DUP ON SWAP 0 DO TEMPO WAIT LOOP OFF dur key Here is an explanation of what is happening in the definition of KK First the key value left on top of the data stack is duplicated for later use by the word OFF The midi key is turned on The duration value is brought to the top of the stack to set the number of executions of the DO LOOP The loop loads the counter with TEMPO and waits for it to count down It does this n times where n dur thus the loop lasts for n beats Finally upon exiting the loop the key is turned off To include rests in your musical phrase just use the inner loop of the KK word to define the following word AA 0 DO TEMPO WAIT LOOP duration Using KK and AR one can then easily create m
7. n Reads the value n found at the Data Queue pointer Marks the current Time Q pointer location as the end of the Queue analogous to double bars at end of a music score Moves the Time Queue pointer to the end of the Queue to the double bar mark Used before appending more events to the Queue X y Z Moves any numbers In the Data Stack to the Data Queue preceded by a word count Leaves the Data Stack empty n X y Z Using n as the Data Queue location of a word count moves data from the Data Queue to the Data Stack 16 TIME QUEUE COMPILING AND PLAYING See Appendix 1 for more on how to use the Time and Data Queues CYCLE PLAY START PLAY TILL PLAY N Use X y z word The word following the caret is loaded into the Time Queue along with the current value of TIME Any data on the Data Stack is loaded into the Data Queue leaving the Data Stack empty Caret can be used both in the execution mode and within colon definitions After starting the timer with TEMPO this program reads through the entire Time Queue When it finds a Time Queue entry for which the queues TIME value is equal to the current TIME value the entry is executed Before leaving TIME is incremented by one Used as part of the PLAY word PARAMETER variable holding the TIME value at which the PLAY routine will start executing PARAMETER variable holding the TIME value at which the PLAY routine wil
8. tine Into the insert buffer then removes the line from the screen Copies the given string if any into the find buffer then searches for the string in the current screen end n Global search for a given string Copies the following string If any into the find buffer then searches for the string starting at the current screen and ending at end If found editing screen is left on the stack Used after F Erases backwards from the cursor position all characters as given In the find buffer Copies the given string if any into the find buffer finds first occurrence of the string then deletes it Copies the given string if any into the find buffer then deletes all characters up to and including the string Copies the given string if any into the insert buffer then inserts the string behind the cursor E and I Replaces a found string with a given string or the contents of the insert buffer List the current screen Make the next Screen current Make the previous screen current n Start editing from line n of current screen 20 APPENDIX A A TIMED FORTH The Glossary contains a great many FORTH words designed to give you control over most of the sound generating devices in the studio The question that arises now however is how to extend this control over time to create musical events PLAYING THE TERMINAL KEYBOARD The most direct
9. 0 to 319 and Drive B accesses Screen numbers 320 to 639 The Editor does not work directly with the screens stored on the disks The screen to be worked upon is first loaded from the disk into one of 2 memory buffers The buffer then is what is actually being worked 4 upon Whenever a new screen is loaded the system will automatically check the screen buffer it is overwriting If this buffer contains an edited version of a screen then the floppy disk is loaded with the new version of the edited screen before the buffer is overwritten At the end of an editing session you must force disk drive updating by executing the word FLUSH so that any changes made to a screen are sure of being saved onto the floppy disks Other than this the disk reading and writing functions are invisible to the user so much so that the disk drives almost appear as a simple extension of the micro s memory space The Editor vocabulary is included in the set of words appended to the RSC dictionary after startup The Editor words are in a separate Vocabulary which must be opened with the word EDITOR before you can access them A description of the Screen Editor used here can be found in the book Starting Forth Some useful words have been added to this Editor vocabulary and are described in the dictionary part of this manual Here are some commands which you will find useful in your editing sessions INIT EMPTY BUFFERS n LIST n LOAD n m THRU nmINDEX n N
10. 60 TO VEL 4 HEX 8000 TO T HEAD A000 TO D HEAD DECIMAL 5 T INIT D INIT MIDINIT 6 7 The piece 8 0 TO TIME 50 ON 56 ON 66 ON 9 32 DUR 50 OFF 56 OFF 66 OFF 10 3 PROG 1 TO PULSE 11 40 TO TIME 50 40 AND DUP Z1 ON 12 104 TO TIME Z1 O OFF 13 40 TO TIME 8 62 N864 N 8 64 N4 65 N 32 68 N 14 40 TO TIME 1656 N 1654 N 1652 N 15 40 30 AND TO TIME 0 0 DAC 20 DUR 0 40 DAC 25 In the initialization part of the screen a tempo is set defining the number of milliseconds to a beat Then the Midi parameters of channel number and key velocity are set Next RAM memory blocks are appropriated for two queues a Time Queue and a Data Queue The values given in the above program line set up 8K byte queues which should be large enough most pieces Finally the Queues are initialized and the midi port is set up for sending Midi data Now we are ready to compile some timed events The word compile is used in the sense that the words and data are not executed but are stored for later execution into the Data and Time queues The TIME variable is set throughout the piece The value of TIME determines the beat number at which the compiled words will be executed when later played It can be set in various ways directly as in lines 8 11 12 13 and 14 through the word DUR which adds a duration to the current TIME value lines 9 and 15 or through a program as with the random number generator in line 15 Each word to be compil
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12. EW 40 0 FORMAT n BACKING ab COPY n REP n PRINT P ON P OFF HEX C 18 If the disk does not seem to be accessing the right screens and you are sure you are in DECIMAL mode use this word If you completely botched up a screen edit and don t want it to be put on disk execute this word Loads screen n into the buffer and lists it out on the terminal Executes any words in the screen and Compiles into the Dictionary any colon definitions on the screen Does a LOAD of screens n thru m inclusive Lists line zero of screens n thru m inclusive Start editing on line n of the current screen To format a disk put it in Drive A and execute this Copy Drive A screens 0 to n to disk in Drive B Copy screen a to screen b Copy screen n in Drive A to disk in Drive B Print screen n onto printer set to 300 baud Baud 300 Send to printer everything going to terminal Baud 1200 Stop sending to printer Change Baud rate to 4800 the max for this machine MEMORY MAP This microcomputer has 64K bytes or memory space 16K or that is taken up by the RSC Forth dictionary and kernel and another 8K is taken up by the Editor and Music Application words in ROM About 32K of RAM memory Is available for dictionary expansion and data If more memory is needed a BANK of memory can be installed for up to 64K of added space A figure of the memory map is shown on the next page Memory locations are given in hexadecimal and the number of bytes in a
13. a good part of this manual is devoted to explaining how to use these new words Two manuals have been left in the studio to help you learn how to use the language The RSC FORTH USER S MANUAL is the manual for this specific microcomputer The first 5 chapters contain a tutorial on Forth The remaining chapters deal with specifics of the micros system which you will not need to know since words have already been created to deal with system details Appendix A contains a helpful summary of the words found in this micro s Kernel Dictionary All the words shown in the Appendix are stored in non erasable memory and thus are always available for you to use The second book STARTING FORTH is a tutorial on Forth programming Not all the words described in this book will be contained in the RSC micro s dictionary though most of them will be You can check the Appendix of the RSC USERS MANUAL to determine whether a specific word is in the dictionary or not STARTUP When you first turn on the Forth Microcomputer the greeting RSC FORTH v6 1 should appear on the terminal screen You should also get an OK reply from the computer after pressing Return and whenever the micro has completed execution of a word If you are getting garbage on the terminal check to see if the terminals baud rate is set to 1200 Upon Startup you have only the dictionary of RSC Forth words as described in the RSC Manual to work with Execute VLIST to see a listing of this dictionary In
14. ange of 0 to 65 535 16 bit number 29 THE RAMP MODULES Most of the Hybrid s programmable parameters are ramps these include the waveform mix the lowpass filter s cutoff frequency transposition or FM depth control the X pan Y pan and the volume For these parameters the programmer must specify both a final value and a ramp speed Both values are limited to a range of 0 to 15 The following table gives the 16 possible ramp speeds VALUE RAMP RATE TIME FOR FULL RAMP 0 1 5 levels sec 0 seconds from level 0 to 15 1 2 4 6 3 2 3 75 4 0 3 6 0 2 5 4 9 45 1 6 5 15 0 1 0 6 24 0 63 7 37 5 0 40 8 60 0 25 9 94 5 0 16 10 150 0 10 11 240 63 milliseconds 12 375 40 13 600 25 14 945 16 I5 1500 10 There is one exception to the ramp values given above for volume decays the rates are half the values shown and the times are twice the value The ramp control voltages are available from 24 jacks on the Hybrid s front panel Each jack is marked as belonging to a single hybrid parameter and voice number The control voltages at these Jacks range from zero to 10 volts They can be patched to the control voltage inputs of any of the analog synthesizers in the studio thus giving you some computer control over the analog synthesizers THE PITCH MODULE P The pitch module outputs a control voltage to a voltage controlled oscillator which is used in cycling through the waveform memories This parameter controls the pitch of the wavefor
15. brid s module polling system to check for completion of the delay To get a delay of t seconds load a value of 100 t 32 MODULE POLLING If the user is to program sound events using the Hybrid timers and ramping controls they must have someway of finding out when the ramps have finished ramping and when the timers have completed their time delays lays A module polling system has been setup to facil tate this The hybrid can beset up to poll all the ramp modules and the timer modules at an extremely fast rate 4 million modules per second It steps through the modules testing each one for completion of a ramp or time delay When it finds a completed ramp or time delay the polling stops and a computer interrupt signal is generated It is then up to the programmer to react to this Interrupt signal The number of the module at which the polling stopped can be read from a specific computer address The programmer reads that location performs whatever actions are desired and then enables the polling again If for some reason the programmer does not want a certain module to stop the polling action when it completes its ramp or time delay they can sat a flag called a MODNASK Module Masking bit Each module has a MODMASK flag When it is set the polling will pass over that module without checking for a completed ramp or time delay S13L 3 32 04 32430 oi 043 U03 SIN 242M E 1043u0 ka k UOTIETNpO 1043U09 Pow Mi
16. cience While there he worked closely with the composer Salvetore Martirano to put together an elaborate performer oriented electronic music synthesizer which became known as the Sal Mar Construction At the time it was one of the few electronic music instruments to allow real time performer interaction with the Instrument The Oberlin Hybrid Synthesizer is an offspring of the Sal Mar In fact Sergio Frances PhD dissertation Hardware Design of a Real Time Musical System serves well as documentation for both the Sal Mar and the Hybrid Synthesizers circuit modules The main difference between the two machines lies in their performer to machine interface The Sal Mar Construction used a large panel of multitudinous switches and knobs at which the performer sat like a grand wizard The Hybrid Synthesizer has hardly any knobs and its only switch is an On Off switch The only way to play the instrument is through a computer program This gives the performer a malleable interface The Hybrid synthesizer like the original Sal Mar can be played in real time by a performer but it can also be automated by the computer or controlled by a combination of the two Thus the Hybrid has the advantage of being adaptable to many different playing situations THE HYBRID SYNTHESIZER VOICE The Hybrid has four identical voices Figure One shows a block diagram of a voice It consists of a voltage controlled oscillator which cycles through two waveshape memories The two wave
17. cluded in the machine is a non erasable memory chip containing additional words for an Editor and Music Applications In order to add these words to the RSC Forth words available at startup you must type the following 22881 EXECUTE return Check out your dictionary now with VLIST The new words are described later in this manual If the micro ever gets stuck while executing a word you can press the RESET button to interrupt it Upon RESET the startup greeting will be displayed but you will not lose any of the words you defined before the Reset If RESET does not un stick the machine then you must do the following remove any disks from the disk drives turn off the power to the micro wait 20 seconds and turn the power back on In such a case you must start over Any words you defined before are lost DISK DRIVE AND EDITOR When creating your own words the dictionary is automatically extended into RAM memory erasable memory thus your words will not remain in the system after you turn off the power To keep your applications and data you must save them on floppy disks using the Editor vocabulary An explanation of how to use the Editor is contained in the book Starting Forth Here I will give you a few details of how the disk editing works The drives use 5 1 2 inch floppy disks double sided double density All the Editor words and the Disk utility words work with 1024 byte memory sections called Screens Drive A accesses Screen numbers
18. computer delay is a simple DO LOOP 35 ON n 0 DO LOOP 35 OFF The note is turned on and then the computer runs around in a circle n times doing nothing but wasting time after which the note is finally turned off The duration of the note is determined by n The word DELAY is such a simple looping delay 35 ON nDELAY 35 OFF This timing method is useful for simple applications but it has two drawbacks First of all changing the tempo of a piece is extremely inconvenient one has to go through the entire piece editing all the DELAY values Secondly time is a valuable commodity in programming The DELAY word causes the computer to waste a lot of time which could otherwise be spent doing more useful things One alternative to the simple loop delay is a hardware counter The RSC Forth micro has such a device a 16 bit counter connected to a 1KHz clock The user loads any 16 bit number n into the counter upon which the number is decremented once every millisecond After the counter is loaded the micro can go off and do other things while the counter spends n milliseconds decrementing towards zero The programmer has only to check the counter for a zero count every once and a while The word T shown below can be used for such a check It returns a non zero flag when the counter is found to have reached zero HEX T 11 CO 20 AND TERMINAL OR 23 A number of words see TIMER WORDS in the word glossary have been created for use with the
19. cycle of a waveform The waveform cycles are repeated at a rate set by the voltage controlled oscillator The user can load any of 64 different waveforms into waveform Memory A and or Memory B at any time Two of the waveforms are internally set and always available to the user Waveform 63 is whitenoise and Waveform 62 is a random complex waveform All other waveforms must be loaded by the user To load a waveform into the voice s waveform memories you must specify the Waveform number and the memory A and or B you want to load it into The change will take place immediately To load a user defined waveform into the general waveform memory first load the wave number times 64 then load the 32 waveshape samples one at a time each sample is limited to a range of 0 to 15 Please use only waveshape numbers 0 through 31 THE WAVEFORM MIXER MODULE M This mixer has the rather specialized function of mixing the outputs of the two waveform Memories A and B This is a ramp function so that the voice output can be dynamically panned between two different waveforms A ramp endpoint value of zero sends only Memory A s waveform to the output A ramp endpoint value of 15 sends only Memory B s waveform to the output Any value inbetween 0 and 15 sends a mixture of the two waveforms If another voice is patched to waveform modulate the voice then the mixer parameter changes its function as did the Transposition FM depth parameter to modulation d
20. ed is preceded bY the percent symbol the caret word can be used if the screen is edited only with the editor word NEW Note that the word immediately following the percent is not executed butis loaded into the Time Queue along with the current TIME value Also when the percent word is executed all numbers on the data stack are assumed to belong to the compiled word and thus are placed Into the Data Queue and a pointer to that data is placed in the Time Queue The data stack is empty when the percent finishes its compiling Words not preceded by a caret or a percent sign are executed as usual An example of this is on line 11 50 40 AND DUP ZI What is happening here is that the key value for the Note On command is generated by a Random Number Generator This key value must be saved for a later Note Off command but it cannot be left on the stack since the compiling word in ON will empty the stack Therefore it is stored in the variable Z1 to be called back prior to OFF on line 12 26 Virtually any executable word can be compiled into the Time Queue by preceding the word with a caret and leaving its required parameters on the data stack At the same time the compilation process can be aided by regular executable words to help set the TIME values or load the data stack The caret can also be used inside a colon definition which allows you to create words to help automate the compilation process as seen in the word N found on lines 13 a
21. epth control Waveform modulation is a rapid panning between the two waveforms Modulation depth then sets how far the panning varies around a central mix value Note that if one of the waveforms is a constant zero then the waveform panning becomes simple amplitude modulation AM LOW PASS FILTER MODULE L This is a voltage controlled filter with a variable cutoff frequency The cutoff frequency is varied through a ramp function The filter is setup to track the pitch value so that the cutof 31 frequency is always a specified distant from the pitch frequency of the note It is that distance from the pitch frequency which is changed through the ramping filter parameter By making the filter track the pitch value the waveforms timbre remains constant over the entire pitch range changing only when the cutoff frequency parameter is changed There are also manual filter response filter 0 controls for each voice located on the Hybrid s front panel THE VOLUME CONTROL MODULE V After the filter the voice signal goes through a voltage controlled amplifier which sets the overall volume of the signal This is a ramp parameter A zero endpoint value completely shuts off the output signal and a value of 15 results in maximum signal strength Since the volume control is a ramp this module can act as an envelope generator by simply stringing several volume ramp commands together THE X Y LOCATION MODULES X Y Each voice of the Hybrid can be
22. g program to obtain time delays Program loops around n times doing nothing before continuing with the next executable word Part of a more elegant delay program Loads the variable TEMPO into a IKHz counter which immediately starts to decrement by one every millisecond Programmer is free to go off and do other things while the counter is counting down A useful word not included in the ROM would be the following HEX T 11 C 20 AND TERMINAL OR f Leaves a non zero flag if either the counter has reached zero or the user has hit any terminal key Program loop which waits for the IKHz counter to reach zero n Loads n into TEMPO and then waits for n milliseconds 15 TIME AND DATA QUEUE WORDS See Appendix A for more on how to use the time and data queues T HEAD D HEAD T D T INIT D INIT FIND II IDATA DATA PARAMETER variable holding the memory location of the start of the Time Queue PARAMETER variable holding the memory location of the start of the Data Queue addr Variable holding the address of the Time Queue pointer addr Variable holding the address of the Data Queue pointer Initialize Time Queue pointer to T HEAD Initialize Data Queue pointer to D HEAD n Load n into Time Queue and increment its pointer n Load n Into Data Queue and Increment Its pointer n Reads the value n found at the Time Queue pointer
23. l stop executing Plays the Time Queue for all time events starting at PLAY START and ending at PLAY TILL Tempo is determined by the value store in TEMPO duration key Midi Note compiler Compiles and loads a Midi Key On and Key Off event into the Time and Data Queues with the current TIME value The TIME value is incremented by the given duration 17 HYBRID SYNTHESIZER WORDS See other documentation for description of the Hybrid Synthesizer MO MI M2 M3 final value ramp speed Wave Mixer Pan or MXM Depth LO L1 L2 L3 final value ramp speed Low Pass Filter TO T1 T2 T3 final value ramp speed Transposition or FM Depth XO X1 X2 X3 final value ramp speed X Location pan YO Y1 Y2 Y2 final value ramp speed V Location pan VO Vi V2 V3 final value ramp speed Volume PO P1 P2 P3 pitch Pitch WO wi a b waveshape W2 W3 Waveshape is loaded into Memory Ai a b 1 into B if a b 2 and into both A and B If a b 3 TMO TM1 time TM2 TM3 Loads 16 bit timer with time value FM x y Volce x set up to Frequency modulate voice y MXM uy Voice x set up to Waveform Mixer modulate voice y MODULATE voice Starts the modulation of voice as set up with FM and MXM MODULATE OFF Turns off modulation in all four voices H INII POLL MODMASK Initializes all the Hybrid voices No modulation No volume Location 0 0 Pitch A440 N
24. m It is a non ramping control with a range of 0 to 255 thus a total of 256 pitches can beset by the pitch parameter The pitch of the output waveform changes in quarter tone increments with the value zero corresponding to approximately 5 15 hertz and the value 255 corresponding to approximately 8 1 Khz The accompanying table shows the note and frequencies corresponding to each of the 256 pitch values A tuning adjustment for each voice can be found on the front panel of the Hybrid Be sure the transpositon module is set to zero before attempting any tuning 30 THE TRANSPOSITION MODULATION DEPTH MODULE T This is a double function module controlling either the pitch or the modulation depth It is a ramping module When used as a transposition control it odds an additional control voltage to the voltage contolled oscillator Thus you can use it to transpose the pitch of a voice or to add frequency glissandos to a note using the slower ramp speeds When other voices are patched to frequency modulate the voice this module changes its function to that of modulation depth control Since the control is still a ramp function the FM depth can be dynamically changed by using different ramp rates THE WAVEFORM GENERATOR W The Hybrid voice is cantered around a digital waveform generator There are two waveform memories each holding 32 four bit samples A figure shows an example of one cycle of a possible waveform Each memory holds one complete
25. mbered zero to seven Use as a PARAMETER variable PULSE Reads and leaves on the stack the Pulse Detect byte n TO PULSE Loads the Pulse Generators with n There are 8 Pulse Detectors and 8 Pulse Generators All 8 are loaded or read from the one word PULSE by assigning a pulse device to each bit in the 8 bit PULSE variable Thus each pulse device Is assigned a weight of 2 where n is O to 7 11 MIDI OUTPUT MIDINIT VEL CHNL MLD ON OFF KPRES CONT PWHL PROG CPRES KK Initializes the microcomputer s port for midi output Must be executed before any midi output activity 1s started A PARAMETER variable holding the current midi key velocity A PARAMETER variable holding the current midi channel number See explanation of PARAMETER word to find out how to load or read the variable n Sends n low byte when the midi transmitter is clear key Sends a Note On command with the current VEL and CHNL key Sends a Note Off command with the current VEL and CHNL velocity key Sends a Polyphonic Key Pressure command with current CHNL value control Sends a Control Change command with the current CHNL most significant byte least significant byte Sends a Pitch Wheel Change command with the current CHNL program Sends a Program Change command with the current CHNL value Sends a Channel Pressure command with the current CHNL dura
26. memory block is in decimal Shaded sections of the map indicate ROM memory also known as Read only or non erasable memory All other sections are RAM memory or read and write memory Several blocks of RAM memory are free for use by the programmer 256 bytes at hex locations 200 2FF 3040 bytes at hex locations 420 FFF 22 520 bytes at hex locations 8000 D7F7 The Dictionary expands upward into RAM memory starting at hex 6000 All other locations are reserved for system use Writing into locations reserved for the system use can crash the system forcing you to start over again This is inconvenient but not fatal to the microcomputer so you are welcome to poke around as much as you want One of the best features of Forth is that the inner workings of the language and of the micro implementing the language are completely accessible to the programmer RSC FORTH MEMORY MAP 6000 7FFF 8192 DICTIONARY RAM 8000 9FFF 8192 RAM time queue AOOO BFFF 8192 RAM data queue C000 D7F7 6135 RAM D7F8 DFFF 2056 TWO EDITOR BUFFERS 000 05D 93 SYSTEM STUFF 05D 100 160 DATA RETURN STACKS 100 1FF 256 EXTERNAL DEVICES 200 2FF 256 RAM 300 420 288 USER VARIABLES WORD DICTIONARY There are two main dictionary sections One is the RSC Forth dictionary as described In the Users Manual and which contains all the standard Forth words as well as those words specific to this microcomputer Also included is a 6502 Assember The second dictionary section con
27. minal key to be hit before continuing on with the next sound event 2K KEY SP Interspersing the sound events with the word K allows the user to tap out the timing on any terminal key For example E1 K E2 K EI K EI K E2 You would probably want to place such a piece on an Edit Screen so that it can be easily re played by executing n LOAD or for longer pieces n m THRU and also so that it can be easily edited For a more intelligent keyboard use the CASE word see the RSC Forth Manual page 6 3 First set up your individual sound events as words El E2 E3 E4 Then define SOUND as the following Case statement CASE SOUND QUIT El E2 E3 E4 E5 E6 E7 TASK TASK The word for actually performing the sound events is as follows PERFORM BEGIN KEY 48 DUP 9 IF DROP ELSE SOUND THEN AGAIN To play the piece execute the word PERFORM Now whenever you hit the terminal key 1 the word El Is executed When key 2 Is hit E2 is executed and so on The word TASK is a do nothing word for use when Keys 8 and 9 are hit and the IF statement in the definition of PERFORM takes care of all other possible terminal keys being struck Finally lets not forget how you stop the program hitting key zero will execute the word QUIT to exit the program s BEGIN AGAIN loop 22 COMPUTER GENERATED DELAYS It is possible to completely automate the timing of an event by having the computer generate the timing delays The simplest
28. nd 14 It is defined as follows N SWAP gt A DUP gt A ON A A DUR OFF duration key This word accomplishes the same function as the word KK except that it is used to compile Midi Key On and Key Off commands into the Time Queue instead of executing them It is recommended that all compiling words have the caret as the first character of its name The N word simplifies the process of compiling monophonic lines into the queues Lines 13 and 14 of the screen show how the word is used The TIME value is set for the start of the monophonic line From then on the word N automatically updates the time with its internal DUR word On line 14 the TIME is reset back to the beginning of the first phrase and a second polyphonic voice is set up using N To start the Time and Data Queue compilation you merely execute the screen lines by loading the screen with the command n LOAD More than one screen can be loaded with n m THRU Once the timed words have been compiled Into the Time and Data Queues you are ready to play the words 0 TO PLAY START n TO PLAY TILL PLAY First set the time segment you want to play by loading the starting time and ending time into PLAY START and PLAY TILL Then you simply execute the word PLAY Hitting any terminal key will stop the play routine and print out the TIME beat at which you stopped You can repeat the word PLAY as often as you want The tempo can be changed by loading a new TEMPO value before execu
29. o transposition Random waveshape Filter closed Zero poll Zero modmask If f 0 stop polling after next data load If f 1 resume poll f if f 0 turn next loaded modules modmasks off If f 1 turn next loaded modules modmasks on EDITOR LIST SHOW INDEX PRINT P ON P OFF LOAD THRU WIPE BULKCLEAR FLUSH COPY REP BACKING BACKUP n lo hi lo hi lo hi n lo hi sre dest n n 18 Lists screen number n Lists screens lo to hi Will stop on keying Lists line zero of screens l to hi inclusive Prints screen n Baud rate 300 Sends all terminal activity to the printer Baud rate 1200 Stops sending to the printer Loads screen number n complies or executes Screen zero cannot be loaded Loads screens lo to hi inclusive Clears screen number n Clears screens lo to hi inclusive Writes all updated disk buffers to the disk Copies source screen to destination Copies screen n to same place on second drive Copies screens 0 to n to second drive Copies drive A disk to drive B disk EDITOR T P TILL NEW 19 n Types line n of the current screen Copies the given string if any into the Insert buffer then puts a copy of insert buffer In the current line Same as P only it puts a copy of the insert buffer In the line under the current line Copies the current
30. onophonic MIDI note sequences PHRASE 5 35 KK 5 36 KK 5 30 KK 5 AA 30 35 KK As an added attraction the tempo for the above sequence can be readily changed since the durations have been defined as numbers of beats the basic duration stored in TEMPO To load a new tempo execute n TO TEMPO and to read the present tempo execute TEMPO 24 A TIMED FORTH The KK word demonstrated above is limited to Midi Key events and to monophonic sequences Of course similar words could be defined to take care of other types of sound events but what is really needed Is a generalized timed Forth capability where any defined word or words can be executed at any specified time A vocabulary of words have been created for just this purpose To demonstrate lets go through a typical programming session using the Timed Forth words We will use the Editor to load the piece onto a Screen Before that however a few words must be defined 0 VARIABLE Z1 0 VARIABLE Z2 COMPILE A couple variables are created to be used as temporary storage of note parameters and a new name is given to the caret word My apologies for this inconvenience for some reason unknown to me most of the Editor words except for NEW do not perform correctly with the caret name Now you can execute the word EDITOR to bring up the editors vocabulary and start loading the following screen Sample Timed Forth Application 1 2 initializing procedures 3 100 TO TEMPO 0 TO CHNL
31. s incremented at the end of the cycle and then the Play program waits for the Tempo timer to count down to zero again before cycling again through the Time Queue Combinations of the event timing methods discussed above are possible Keep in mind that the events in the Time Queue are executed one after the other Hopefully the words are executed fast enough so that those events which are suppose to happen simultaneously will sound that way even though In actuality this is not the case On the other hand you may want to insert one of the delay words discussed in the second section of this appendix as part of the time queue Keep in mind that if this is done the TIME values will not reflect the true times You may even want to insert terminal keyboard control words into the queue using the K word described in the first section Or you can create words which act upon Input pulses or input ADC values In this way you can shape not only the sound events but the performance medium as well 28 THE OBERLIN HYBRID SYNTHESIZER INTRODUCTION The Hybrid Synthesizer is a four voice electronic synthesizer designed to be controlled from a computer It is currently interfaced to the RSC FORTH Microcomputer a 6502 based microcomputer with a ROM based Forth language The synthesizer was designed and built here at Oberlin in 1973 1974 by Sergio Franco Before coming to Oberlin Sergio Franco was at the University of Illinois completing a PhD program in Computer S
32. shapes are mixed together and sent through a low pass filter with a controllable cutoff frequency After the filter the signal goes through a voltage controlled amplifier to set the overall volume Finally pan controls place the signal within a quad space by distributing it among the four synthesizer outputs Any voice can be patched to modulate any other voice The modulation can be frequency modulation or waveshape mixer modulation Notice that if one of the two waveshapes is silence then the mixer modulation becomes simple amplitude modulation A 16 bit timer is included with each voice to facilitate computer controlled timing of the sound events Each voice has ten computer controlled parameters pitch waveshape memory waveshape mixing lowpass filter cutoff frequency volume left right pan front back pan transposition or frequency modulation depth modulation patch and timer delay All but four of the parameters pitch waveshape modulation patch and timer have ramp type parameters You can think of a ramp as a single segment envelope generator The parameter value slides from its present value to some end value at a programmable speed The programmer specifies the end value and the speed of the ramp Both the endpoint and the speed for all the ramp parameters are limited to a range of 0 to 15 four bit numbers in digital terms Of the non ramping parameters the pitch and mixer have a ranges of 0 to 255 8 bit numbers and the timer has a r
33. tains Editor words and Music Application words These words were created and placed in a ROM memory to be appended to the RSC dictionary at startup The words contained in the second dictionary section are described in the following glossary The glossary words are grouped by function Each word description is preceded by a data stack use description enclosed by parentheses The symbols at left of the three dashes indicate the order in which any input parameters must be placed on the Forth data stack prior to execution of the word The top of the stack is to the right Also any parameters left on the stack after execution are listed to the right of the three dashes Unless otherwise noted all references to numbers are for 16 bit signed integers Stack values are always 16 bit numbers Note that the Data Stack has a limit of 50 16 bit numbers and the Return Stack is limited to 30 numbers Acknowledgments are due to Allen Strange and Daniel Kelley of San Jose State University who have developed a Forth based synthesizer language called MASC Meta Language for Adaptive Synthesis The dictionary sections on Data Structures and System Exclusive Midi Output are taken from MASC The Random Number Generator words were taken from the book Starting Forth by Leo Brodie The command based Editor was written by Sam Daniels and modified by Dave Boulton The remaining words were written by John Talbert at Oberlin College UTILITY WORDS LSHIFT RSHIFT
34. ting PLAY 27 Timed events need not be compiled in order One only needs to make sure that the correct TIME setting precedes the compilation Events can be appended to the end of the Time Queue by executing the word FIND to find the end of the Time Queue and then proceeding as before with careted words As of now there is no way to directly edit the Queues so It is recommended that you put your piece on edit screens and use the standard screen Editor to work on it To reload an edited version simply reload the screens making sure that you first execute D INIT T INIT if it is not already on the first screen All the words you need to know to use the Timed Forth have been described here Other words found on pages 13 and 14 of the glossary can be used for more ambitious projects which directly manipulate the queues In such cases the following description of the queue formats will be helpful The Data Queue is loaded with blocks of data taken from the data stack The data is preceded by a word count followed by the data itself The Time Queue is loaded with data triplets a TIME value the address of a Data Queues word count zero if there is no data for this word and the execution address of the timed word The end of the Time Queue is marked by a Time value of 1 The Time Queue is played by cycling through the entire Queue and executing those words for which the stored TIME value is equal to the present value The present TIME value i
35. tion key Sends a Key On command with the current VEL and CHNL waits for the specified duration see TIMER section and then sends a Key Off command Useful for monophonic sequencer applications 12 KLR Sends a Key Off command to all 128 keys of the current CHNL YAMAHA DX SYSTEM EXCLUSIVE See appendix B on Yamaha midi codes and masc commands DX7 Sends Yamaha DX7 system exclusive status Used Inside both FPAR and CPAR words FPAR data parameter Sends a Function Parameter change to parameter chnl 1 CPAR data parameter Sends a System Common Parameter change to parameter chnl 1 MIDI CONTROL CHANGES Continuous Controllers value MODWHL Modulation Wheel data range 0 127 BREATH Breath Controller data range 0 127 FOOT Foot Pedal data range 0 127 P TIME Portamento Time data range 0 127 D ENTRY Data Entry Slider data range 0 127 VOLUME Volume Slider data range 0 127 TOUCH After Touch data range 0 127 Switch Controllers SUS ON Foot Sustain pedal on SUS OFF Foot Sustain pedal off P ON Portamento on P OFF Portamento off D Data Entry Switch 1 D Data Entry Switch 13 MIDI INPUT The midi Input runs on an Interrupt system When midi input Is detected the micro stops what It Is doing and runs the assembly coded word gt M after which it returns to the Interrupted process The word gt M receives the midi Input byte and loads It Into a 4096 byte
36. ue n1 in the n data variable of the vector X n X Leaves the value of the n data variable of the vector X on the stack Note that the first element or the vector is 0 X Used to create a 2 dimensional matrix of data values grouped under one name mnHYPARAMETERSX Creates an m by n matrix called X ni TOmnX Stores the value n1 into the m column and nth row of matrix X mnX Leaves the value of the m column and n row or the matrix X on the stack Note that the first element of the matrix is 0 0 X Used to create a vector of executable words grouped under one name N EXPARAMETERS X Creates a vector or n words called X TASK TO n X Stores the location or the word TASK In the n element of the parameter K nX Will execute the word whose location was stored In the n element of X Note that the first element of the vector is 0 X 10 RANDOM NUMBER GENERATOR SEED CHOOSE RND addr Leaves the address or the seed for the random number generator Use SEED to read the seed value and use n SEED to load the Seed with n n x Returns a random number x between zero and n 1 hi lo x Returns a random number x between hi and lo inclusive ADC DAC AND PULSE DEVICES ADC DAC PULSE n x Returns 8 bit value x read from the nth analog to digital converter ADC s are numbered zero to seven x n Loads the low byte of x into the nth digital to analog converter DAO s are nu
37. way of controlling Forth generated events in time is to use the terminal keyboard as a quasi musical keyboard The idea is simply to type in the event and hit return when you want it to occur 34 ON 38 ON return 34 OFF 38 OFF return If you try out the first line don t forget to execute MIDINIT O TO CHNL 60 TO VEL before starting you will find that the two notes are arpeggiated a bit This is because the computer must search through a rather large dictionary of words for each number or word on the line before it can execute the word Now that the notes are sounding another difficulty arises you will have to be able to type In the second line very quickly If you want short note durations To get around these two problems you can take the two lines above and compile them into words El 34 ON 38 ON E2 34 OFF 38 OFF Now all you have to type Is El return E2 return The dictionary search was performed during compilation when the two words were being formed so that now when the computer executes each word it knows exactly where each routine is located because that information is stored In the definition of El or E2 Although the two Note On events of El still occur one after the other this happens so fast less than one millisecond that to our ears the two notes turn on simultaneously 21 For even more control over the timing of the sound events you can create a word which would cause the microcomputer to stop and wait for a ter
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