On 22 Feb 2007, at 21:34, Dilwyn Jones wrote: >> I want to present kind of "demo" for QL on the retro-computing >> competition called Forever see: http://forever.zeroteam.sk >> I did some graphics already on PC and it looks good (looks cool in >> fact >> :-). But, I need to write special screen hadler with following >> conditions: >> >> 1) I need to use both screens of the QL without affecting of the 2nd >> screen by system variables. > 1. Standard QDOS cannot handle the second screen area, system > variables have to stay at address decimal 163840
QL hardware allows two screen areas at $20000 and $28000 which houses the system variables. To use #1, disable QDOS: (i) Go to supervisor mode by TRAP #0 (ii) Disable interrupts by ORI #$0700,SR (iii) Make A7 a suitable value as it may be in #1's memory area. The MCSR byte at $18063 controls the screen Bit Function 1 0 = turn on display, 1 = turn off display 3 0 = mode 4, 1 = mode 8 7 0 = screen 0, 1 = screen 1 Writing to MCSR with 1 in bit 7 should select the second screen. Of course you now can't use most of the TRAP's so you have to write your own routines to access these screens. The above appears in Pennel's Assembly Language Programming on the Sinclair QL. George _______________________________________________ QL-Users Mailing List http://www.q-v-d.demon.co.uk/smsqe.htm
