Re: [cc65] char-copy and interrupts (C64)

Date view Thread view Subject view

From: Ullrich von Bassewitz (
Date: 2003-03-17 19:24:13

On Sun, Mar 16, 2003 at 10:39:47AM +0100, Tim Schürmann wrote:
> It don't matter where you place the charset and the screen (under the kernal): the
> result is the same.

I think the problem is that the memory where you placed your text screen is
not readable (a read will return the ROM contents, not the RAM contents). On
the C64, the cursor is controlled by software. The character under the cursor
is remembered and periodically inverted in the ROM interrupt handler. If the
character at the cursor position cannot be read, you will get erratic results.



Ullrich von Bassewitz                        
To unsubscribe from the list send mail to with
the string "unsubscribe cc65" in the body(!) of the mail.

Date view Thread view Subject view

This archive was generated by hypermail 2.1.3 : 2003-03-17 19:24:23 CET