Re: Optimiser and memory mapped I/O

[Peter Barada <pbarada at mail dot wm dot sps dot mot dot com>]

>which it would be if 0xfe8001 and 0xfe8003 were normal memory locations. 
>The problem is, they aren't; they are I/O maps. Write to 0xfe8001 is 
>used for register select, and 0xfe8003 gets the actual value of the 
>register. Any ways around this (besides not optimising at all)?

Use 'volatile':

  *(volatile char *)0xfe8001= 0x4;       /* call msg at level4 */
  *(volatile char *)0xfe8003= 0x6;       /* generate vector, edge interrupt */

  *(volatile char *)0xfe8001= 0x6;       /* timer interrupt level 6 */
  *(volatile char *)0xfe8003= 0x0;       /* level interrupt */

  *(volatile char *)0xfe8001= 0x2;       /* parallel interrupt level 2 */
  *(volatile char *)0xfe8003= 0x2;       /* edge interrupt */

  *(volatile char *)0xfe8005= 0x18;      /* vectors $18, $19, .. $1F */

  *(volatile char *)0xfe8007= 0xff;      /* enable all interupts */

-- 
Peter Barada                             Peter.Barada@motorola.com
Wizard                                   781-852-2768 (direct)
WaveMark Solutions(A Motorola Company)   781-270-0193 (fax)

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