Scor­pio News

  

October–December 1988 – Volume 2. Issue 4.











Page 22 of 35











I have modified my BIOS so that screen paging is OFF when the system boots. By typing ^TS the screen paging flag is set to restore paging, and most of the SYS paging commands are operative. The problem with the SYS method was that if paging had been turned off, a Warm or Cold boot was needed to restore it. With my method it can be turned ON or OFF at will. The BIOS screen paging routine has been further modified so that control characters are needed to control the paging options. (ie; ^C, ^S, ^R, ^K). The Space key is the only exception, and this functions as in SYS. The ‘W’ option is now redundant.

Screen Dump control (^TD) has been transferred to this function, rather than from EDIT mode, so that it is universally available.

No originality is claimed for the various support subroutines in the listing, but I have included them to show how they inter-relate with the direct keyboard commands, or how extra space can be saved.

The routine SIVCMD is used to send command strings to the IVC/SVC. It saves a considerable amount of code overall compared multiple blocks of code like –

LDA,ESC
CALLCRTA
LDA,'M'
CALLCRTA10 bytes

The above is replaced by –

CALLSIVCMD
DBESC,'M',06 bytes

The actual routine SIVCMD only takes 8 bytes, so if more than two blocks like the first example above are used, there is a real saving in BIOS size, allowing room for more features.

The clock routines listed are for the MAP80 R.T.C. card, which is a small card that shares the Printer Centronics port. I use several of these cards, at home and at work, and they are very successful, keeping good time, and not interacting with printer operation or being corrupted by it in any way. The main benefit of this card is that it does not require an extra port. I have also successfully used the RTC on the GM816 I/O card for this purpose. I was not able to overcome the clock corruption problems when I tried the GM822 RTC card, some years ago. I have added an extra ‘JUMP’ to the jump table at the start of the BIOS, so that the clock routine can always be found by external programs, by calling this address at BIOS + 33H. On EXIT from the clock routines, HL contains the address of the Date and Time string so that it can be found by external programs.












Page 22 of 35