From: robertapengelly@gmail.com   
      
   On Saturday, 11 November 2023 at 11:41:08 UTC, wolfgang kern wrote:   
   > On 11/11/2023 11:18, Robert Pengelly wrote:   
   > ...   
   > > "have you enabled IRQ4 in the PIC port 0x20"   
   > > I looked at your table stuff but I'm still a little confused how I enable   
   it.   
   > only modify one:   
   > in al,0x21   
   > and al,0xEF ;reset bit 4   
   > out 0x21,al   
   >   
   > or all if your brave :)   
   > mov al,00   
   > out 0x21.al ;enables all 8 channels   
   >   
   > and before you touch any part of the interrupt chain you should disable   
   > IRQs with this single byte reserved for that, re-enable after done.   
   > > As for the code all I'm doing is changing my timer interrupt to the IRQ4   
   one (0x0C * 4 (+ 2) as that's what I think that's what the interrupt get   
   fired).   
   > [PIT(timer)] fires IRQ_0 (INT08) at default setting 18.2 Hz then:   
   > * PIT handler (either BIOS or DOS or your own) may satisfy the PIT by   
   > reading port_0x40 (not required if set to auto repeat mode, default).   
   > * PIT handler also increments the TIMER-variable   
   > altering this may cause the system to hang.   
   >   
   > [COM1 at IRQ4 aka INT!2] fires on your chosen serial-event.   
   > * I'd chose INT on Buffer full for a mouse   
   > * the mouse may send several bytes and each cause an interrupt, so   
   > * the IRQ4 handler must read the com-port and must be aware of how many   
   > bytes may come in addition so it fills a buffer (where is yours?) and   
   > then respond to the result (can be button/wheel/x/y-motions or error).   
   >   
   > I never abused the PIT-handler for a test, this is not good practice.   
   > __   
   > wolfgang   
   Awesome it works thanks.  As for:   
      
   and before you touch any part of the interrupt chain you should disable   
   IRQs with this single byte reserved for that, re-enable after done.   
      
   Do you mean some like if I want to do something like:   
      
   mov  [0x33 * 4], offset handler   
   mov [0x33  * 4 + 2], segment   
      
   then I should disable the IRQ first then re-enable it after I setup the   
   interrupt.   
      
   As for the timer I'm using a handler for int 1Ch, is that bad practice or   
   something?   
      
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