Difference between revisions of "84PCE:Ports:0020"

Revision as of 21:29, 26 August 2016

Port Number: 0020-0025

Function: Memory Protection Range

0020-0022: Memory protection range lower limit (LSB in 20, MSB in 22)

0023-0025: Memory protection range upper limit (LSB in 23, MSB in 25)

Any memory access at an address (after adding MBASE in z80 mode) in this (inclusive) range has the following effects:

@@ Line 4: / Line 4: @@
 '''Port Number:''' 0020-0025
-'''Function:''' Flash Protection
+'''Function:''' Memory Protection Range
-This range of ports controls access to flash so that you don't accidentally do something really really bad. Information is not public on the actual control of these ports.
+-0022: Memory protection range lower limit (LSB in 20, MSB in 22)
+-0025: Memory protection range upper limit (LSB in 23, MSB in 25)
+Any memory access at an address (after adding MBASE in z80 mode) in this (inclusive) range has the following effects:
+* Reads always read-as-zero.
+* Writes don't affect the byte in memory and cause an nmi.