Tristan Mumford wrote:
Michael J. Mahon wrote:Tristan Mumford wrote:One thing about the RAM card struck me as odd. The read and write LEDs. What kind of superhuman could actually see them during a memory access? I also like its red IC sockets.The read and write LEDs indicate modes of the card. If the card is disabled (and ROM is enabled), then both LEDs are out. If the card is enabled for reading, but write-protected, then the read LED is on. If it is enabled and write-enabled, then both LEDs are on.How is the memory write protected?
It is a software-controlled softswitch on the card. Accessing $C0s0 (bank A) or $C0s8 (bank B) enables the card for read-only access. Accessing $C0s3 (bank A) or $C0sB (bank B) enables the card for read-write access. (The bank switching refers to the 4K space addressed as $Dxxx.) Check the "Language Card" or "16K card" manual for more info. -michael NadaNet networking for Apple II computers! Home page: http://members.aol.com/MJMahon/ "The wastebasket is our most important design tool--and it's seriously underused."