Scor­pio News


April–June 1987, Volume 1, Issue 2

Page 48 of 51

figure 2, notch or dot towards you. Turn the board co OV and pin 1e to the solder pad of R21 with come ‘have now mechanically secured

4) Insert the 741800, 6 over and solder pil thicken tinned copper wire, “The two wir: the chip to the beard.

5) Interconnect the pine of che 74LS00 connecting wire, single core preferably.

showa in figure 3, using some thin

figure 3.Viring diagran, vieved from component side

5) Now connect the four sdditional Links as follows

Lxa/p to 74LS00 pin 5 (your original mie eteck) tae ttt ae (our 2m clock)

tale 2 5 ot 8 (Output clock)

tesyis* + Lea (clock select Line)

(Per’te 5 pin 18)

or shores.

7) Finally double check all the wiring for any mistal vestiNc

Re-install the FDC card into your system and reconnect the drive cabling. Power up and boot up in your normel disk operating system Everything should work as before, 1f not check the voltege Level on 1c5 pin 15 which should be low. IF rhis ie ok then check that the two clock lines are not svapped. I had 10 problems, everything worked first time when 1 booted up the disk system,


Modifying existing software should be quite straight forward. Changes only need to be made whenever commands that (potentially) move the disk drive’s head are iseued eo the Wp1797 disk controller chip. I include details of 2 versions of software, one where peisitive disk coutines communicate directly with the MD1797 Foc chip and secondly where the routines communicate Indirectly via s single call (1’e SYS users)

Firstly, for routines that send commands to FDC directly, 11st{og 1 shows the raggested alterations (in lower case) to the existing code “The existing code is presented in a hypothetical form, and you may have to alter it slightly in Light SF your own circumstances. The “FDCHUB?” aubroueine call nay in fact be 9 jump fo tome common code shared by “HOME:”, "SEEK:” and aaybe other routiner as well. In this case Just append the source of the ‘stepsiow-’ at the end for your fepeBusy’ routine

This is an OCR’d version of the scanned page and likely contains recognition errors.

Page 48 of 51