Jet-Disc Disc II Drive System
- What is a Jet-Disc
- Board Images
- ROM Image. - WIP - waiting for file.
- Jet Disc Advert
- Jet Disc Advert
- Jet Disc Review Personal Computer News September 1, 1983.
MPE Jet Disc Manual Documentation
- 1. Introduction
- 1.1 Hardware
- 1.1.1 Installing the Hardware
- 22.214.171.124 With MPE ACE motherboard Vr3
- 126.96.36.199 With MPE ACE motherboard Issue 1/2
- 188.8.131.52 Power to the Jet Disc!
- 2. Software
- 2.1 Formatting discs
- 2.2 The directory
- 2.3 Saving and Loading the FORTH Dictionary
- 2.4 Saving and Loading BYTE File
- 2.5 Killing files?!?
- 2.6 More than one drive
- 2.7 Direct disc interface
- 2.7.1 FDC interface
What is a Jet-Disc
Disc Drive Controller A versatile device capable of controlling up to
four independent disc drives, which can be of mixed format. It is
compatible with most makes of 5¼" floppy disc units and can also
be used with some types of 3" drive. The ACE disc drive controller
is designed by Richard Roberts, manufactured and sold directly
by MicroProcessor Engineering back in 1983. Today MicroProcessor Engineering specialises in Real-Time and Embedded systems today see their site for more details and Forth resources. There were two versions of the Jet Disc, I & II.
ROM Image - WIP
To be uploaded as soon as the file has been sent to the archive.
Also in the Boldfield eight page sales brochure January 1985;
Jet Disk press release in Personal Computer News September 1, 1983
MEP Jet Disc II User Guide
The Jet-Disc II system on the Jupiter Ace allows loading and saving of files at speeds far greater than is possible using a cassette link. Jet-Disc II with the Ace is designed to be used with any standard 5" double density drive allowing up to 160 kbytes storage on 40 track single sided drives and 640 kbytes on 80 track double sided drives. It is possible to interface different types of drive to the system.
Jet-Disc II is based around the Western Digital 1 770 Floppy Disk Controller/Formatter chip, and 4 kbytes of EPROM. The WD1770 is a MOS/LSI device which performs the functions of a 5 ¼" Floppy Disk Controller/Formatter. It Is similar to the WD179X, but also contains a digital data separator and write pre compensation circuity. The device controls 5 ¼" drives with data rates of 125 Kbits/ Sec (Bingle density), not used in Jet Disc II and 250 Kbits/ Sec (double density).
1.1.1 Installing the hardware
Due to certain memory requirements of the Jet disc It is necessary to take action so that the top 16 kbytes of memory are not used by RAM packs etc.
184.108.40.206 With MPE ACE motherboard Vr3.
If you are using either a Jupiter 16k RAM pack, this has no decode the upper address line thus has a shadow, or a Boldfield 48k RAM pack: fit a 74LS10 in the DIL pads on the Motherboard, and cut lines a & d and link b & c ( c is not marked but is at right angles to d); this pages out the upper 16k bytes of the MREQ- signal from the two connectors at either side of the motherboard allowing you to place the Jet Disc on the far side.
220.127.116.11. With MPE ACE motherboard Issue 1 / 2
Early versions of the ACE mother board were intended for use with JET DISC I, which had different memory requirements than JET DISC II. Thus some alterations have to be made: Again a 74LS10 is required in the DIL pad, but before fitting cut all the tracks from the DIL pad, solder in a 14 pin socket and connect it to the ACE bus bars as in Fig 1.0
18.104.22.168. Power to the Jet Disc!
At this stage you have to decide if your ACE power supply can power all your expansion hardware, if not, you are going to have to use the disc drive power supply for Jet Disc. I would advise that if you are running more than just the Jet Disc and RAM pack to use external power for the controller, there are fitted at the top of the board connectors for this situation. Now apply power to the JET-BOARD via the 12-0-0-5 Volt connectors then power up the ACE which should then sign on as normal; if this does not happen turn the system off and check as follows:-
That the ACE signs on without the MOTHER board present.
2) If you are using your own power supply, that you have not transposed the 5 and 12 Volt lines, turn off quick !!!!!!!
3) That there are no pieces of metal etc. under the MOTHER board.
4) Any socketed chips have not come loose in transit.
After checking the above turn the system on again. Once the Ace has signed on correctly type
60345 EXECUTE <cr> The ACE should then clear its screen and print: Jet Disc II Rev x.x 1985 Microprocessor Eng. Ltd
If it doesn't, again check the board and also make certain that the
chips (if socketed) are well in the sockets.
The DISC software has been linked into the ACE's FORTH ROM software. This can be proved by typing
VLIST <CR> FORTH RS REDEFINE SD DR# PT BDEL ETE DRIVE ERR DIR WRITE SECT BUF READ DELETE SEEK HOME T/S NS DS AVE DLOAD DBSAVE DELOAD UFLOAT I NT FNEGATE F/ * F+ F- LOAD BVER IFY VERIFY BLOAD BSAVE SAVE LIST EDIT FORGET REDEFINE EXIT ." ( [ +LOOP LOOP DO UNTIL CONSTANT V ARIABLE ALLOT C, , CREATE : DECI MAL MIN MAX XOR AND OR 2- 1- 2+ 1+ D+ - + DNEGATE NEGATE U/MOD * / * MOD / */MOD /MOD U D > U< < > = 0> 0< 0= ABS OUT IN INKEY BE EP PLOT AT F. EMIT CR SPACES SPA CE HOLD CLS 1/ #S U. . SIGN #> <# TYPE ROLL PICK OVER ROT ?DUP R> >R ! @ C! C@ SWAP DROP DUP SLOW FAST INVIS VIS CONVERT NUMBER E XECUTE FIND VLIST WORD RETYPE QU ERY LINE ; PAD BASE CURRENT CONT EXT HERE ABORT QUIT OK
Turn the power off from the system. Check that the drive you intend
to use with your Jet-board is set up to be drive 0. Then plug a ribbon
cable into the drive and Jet-board, again making certain as to which
way round it goes - see Fig 1.1. If you are using 5" drives take power
to the drive from one of the 12-0-0-5 Volt power connectors. Put at
least a 1 kbyte RAM module on to the MOTHER-board. Power up the system
again - remembering to put power to the drives followed by the
Jet-board then the ACE , otherwise the ACE may crash.
Once this stage has been reached place a disc in the drive and type
60345 EXECUTE <Cr> 16 BASE C! <Cr> 0 D000 C! <Cr> DO C000 C! <cr>
You will hear the motor come on the drive.
The head on the drive should now step to track 0, the outer track. If this happens then it means that you have set up your drive and JET-BOARD correctly, we hope!
2.1 Formatting discs
Once you have correctly set up your JET-DISC system load from tape the file FORMAT, place a blank disc in the drive and type
The ACE will then respond as follows:
+ ACE Jet Disc II Formatter | + Do you require verify | Y / N + Which Drive | 0...6 + How many sides | 1...2 + How many tracks | 1...255 + Formatting | .............................. | ........ + | Verifying | | Only if verify | required + Name of disc | cccccccccc Stepping rate | 0...3 + Format Complete | +
N.B. drives 4... 6 are the second side of drives 0...2.
You will hear the head HOME as before but then it will step from track to track filling them with data that will be used to identify them later, after each track the Ace will print a '.'. The drive will then home again and a blank directory will be written (see below). If required the disk will now be verified, most of the time its not worth using the verify option as it takes so long, and errors are very rarely detected! The disc is now ready for use. With 5" 40 track discs, you can store 156 kbytes of dictionary files or up to 160 kbytes of Data. It is possible to fit up to about 200 kbytes of data if you are crafty, see 1770 data sheet for details! Step rate refers to a number which is given to the WD1770 with each command, and defines how fast the head moves on the drive as follows:
Step Rate Step Number WD1770 WD1772 0 6 ms 2 ms 1 12 ms 3 ms 2 20 ms 5 ms 3 30 ms 6 ms
It can be seen from the above table that if you have a very fast drive, you can replace the controller chip with a WD1772, thus producing faster head movement.
2.2 The directory
Place in the drive a formatted disc and type DIR <cr>
DIR cccccccccc x Sides xxxx Sectors xxxx Free Step y
This will display an empty directory as above, the directory contains a number of headers (see below) which identify files. Telling the system how long each file is, its starting track and starting sector. On the Jet Disc there are 16 sectors (1...16) per track. Track #0 is used as the directory track the others are for files. Each file has one block of 16 bytes in the directory which contain the name track sector & length data. As new files are saved, the directory is extended with 10 bytes containing the file name. The file name can be in upper or lower case as in the cassette SAVE word. The directory also contains a bit map which is used to identity any empty sectors in the directory.
2.3. Saving and Loading the FORTH Dictionary
As with the ACE's normal FORTH word SAVE, DSAVE transfers the contents of the FORTH DIRECTORY onto a mass storage device - but at a slightly faster rate!!!
To prove this type in one of your favourite words such as the one below:-
: TEST CR ." Hi there-" CR ." this word was saved on disc!!!" CR ;
Now place a formatted disc in the drive and type
DSAVE TEST <CR>
Again you will hear the drive head move, as the directory will be
written on followed by the head stepping to track 1 sector 1 (the
first free sector) to write the file to the disc. There is no need to
VERIFY a disc file as this is done when using WRITE which is part of
The ACE will then display:
DIR cccccccccc x Sides xxxx Sectors xxxx Free Sectors Step y Dict: TEST 1 1 66 OK
Now FORGET TEST and type DLOAD TEST again the disc head will move, firstly to the directory track, compare the name supplied with DLOAD to that in the directory and step to the file, load it at the end of the DIRECTORY and print OK
DLOAD TEST <CR>
If you now type VLIST you will see that TEST has again appeared in the DICTIONARY, TEST can now be executed in the normal way.
TEST <cr> Hi there- this word was saved on disc!!!" OK
If for any reason the name of the file supplied with DLOAD or DBLOAD (qv) does not exist the ACE will return with ERROR-21, if no file name was supplied ERROR-19.
When trying to save a file that is larger than the space remaining on the drive, or saving any file when the directory on the drive is full then ERROR-22 will be reported.
2.4 Saving and Loading BYTE files
Hard as it might seem to save and load byte files you use DBSAVE and DBLOAD in the save way as you would use BSAVE and BLOAD, gosh!
2.5 Killing files?!?
Once a file has been written to disk you can't write a file of the same name to the save disk until that file has been deleted. The word which allows you to do this is DELETE for dictionary files and BDELETE for byte files. So to delete the file from the last example, type
DELETE TEST <cr>
It is possible to have two files of the same name but of different types on the same disk.
2.6 More than one drive
Jet Disc II can handle directly up to 3 drives, of either one or two sides, or four drives of all single sides. To change drive use the word DRIVE, which takes a number off the stack and makes that the current drive, firstly it stores the top of the in location 09D000, thus changing the physical drive, then attempts to read the first sector of track zero on that drive. From which it will get data on sides per disk, tracks per side etc.
2.7 Direct disk interface
If you wish to do some direct disk interface you can step to the outer track, track 0 with the word HOME, or to track n, with ft SEEK. The current sector number can be changed by altering the single byte number held at the address contained by SECT. The current sector of the current track can be accessed by READ or written by WRITE, data is written or taken from the address returned by BUF.