SB BBC @ GBR Oldie hints/tips #203-204 Hints and tips from the archives of Wakefield BBC Micro User Group... 203. Master/BBC 1772 DFS chip snag ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ There are two possible FDC (Floppy Disc Controller) chips which may be fitted to a Master, or to later Acorn DFS upgrade kits for a BBC B. (BBC B DFS upgrade kits originally used an 8271 chip.) There is the 1770, and the similar 1772. With the 1772, you can have problems using older drives (mainly 40T ones), or 80T drives when used in 40T mode. The configuration command *CON. FDRIVE 0 gives 6 milliseconds track-to-track head-step time on a Master with a 1770 or 1772, whereas *CON. FDRIVE 2 gives 30ms with a 1770 and only 3ms with a 1772! Many older 40T drives are too slow to step the head at 6ms, so cannot be used at all with a Master fitted with the 1772. If an older drive fails to work with your Master, no matter how you configure it, but works on another Master or BBC B/B+, it may be because your machine has a 1772 fitted. (The Master Compact has a 1772 fitted as standard I believe.) 80T drives used in 40T mode, (either by being switched or by fancy software), will not work at 3ms (or possibly not even at 6), as they have to step twice each time, thus effectively trying to step at 1.5ms! See the table on the next page for a summary of the timings. The new alternative MOS ROM for the Master now has additional software delays built-in, and so can effectively handle step times of 3ms right up to 32 ms with a 1772, and 6ms up to 50ms with a 1770. Better late than never I suppose! Acorn now fit the 1772 to their official DFS upgrade kits for the BBC B. With the 8271 and 1770 chips, keeping keyboard links 3/4 'Open' sets the slowest head-step time, but this is not the case with the 1772. The slowest step time available with the 1772 is 12ms, and even this may be too fast for some old 40T drives. Here is a list of link settings for the various Acorn DFS chips; a '0' means 'Open' (OFF) whereas a '1' means 'Closed' (ON). Confusingly, Acorn appear to have transposed all the '0's and '1's in the 1770/2 DFS User Guide Addendum 1, and also in the new supplement sheet 0433,080 Issue 1, the latter kindly supplied to me by Arc Electronics in Wakefield. Trust Acorn! BBC B MASTER 128 Link 3 Link 4 Step Time *CONFIGURE Step Time 8271 1770 1772 FDRIVE 1770 1772 1 1 4ms 6ms 6ms 0 or 1* 6ms 6ms 0 1 6* 12 12 2 or 3* 30 3 1 0 6 20 2 0 0 24 30 3 * without pre-compensation (ADFS) - seems to make little or no difference. * Note that the two settings of the links which set 6ms with the 8271 are not actually identical; the one starred has much longer settle and head load times, and is therefore effectively slower. I can supply further detailed information about the practical aspects of setting these links on request. In summary, a setting of 6ms should be suitable for most modern drives, including switchable ones. However, older drives may require 12ms or more, but modern 3.5" drives will operate happily at 3ms, as on the Arc/A3000. Some modern 80T 5.25" drives will also operate at 3ms, though not when used in 40T mode. In any case, there seems little point in trying to 'push' 5.25" drives beyond 6ms, nor 3.5" drives beyond 3ms. 204. Attractive menu boxes for the BBC Master ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ If, like me, you go green with envy at the attractive menus on the Archimedes, and would like to produce something similar on your BBC Master, then this simple routine may go some way towards helping you. DEFPROCfill produces the patterned background, using VDU23,2 to define the pattern which GCOL16,1 constructs. After MOVEing to the screen origin, the whole screen is covered using PLOT 101 (Rectangle Fill). DEFPROCbox just draws two areas; one in the background colour (in this case black) and one in the foreground colour (white) with the latter offset a little to the left and upwards. The screen might be coloured suitably using VDU19,0,5,0,0,0 and text is best written at the graphics cursor, so a VDU5 and GCOL0,0 (black) will have to be included. OK not quite an Archimedes, but now at least it's the screen that's green, (or blue, or ....). 10 REM Smarten up your Master, by Andrew G8YHI 20 MODE128 30 PROCfill 40 PROCbox(40,700,240,1000) 50 END 100 DEFPROCfill 110 VDU23,2,170,85,170,85,170,85,170,85 120 GCOL16,1 130 MOVE0,0:PLOT101,1280,1024 140 ENDPROC 200 DEFPROCbox(left%,bottom%,right%,top%) 210 GCOL0,0 220 VDU25,4,left%;bottom%;:VDU25,101,right%;top%; 230 GCOL0,1 240 VDU25,4,left%10;bottom%+10;:VDU25,101,right%-10;top%+5; 250 ENDPROC 73 Rick G4BLT @ GB7WRG