84PCE:Ports:003A - Revision history

Jacobly at 04:35, 27 August 2016

2016-08-27T04:35:56Z

PT at 09:26, 26 May 2016

2016-05-26T09:26:47Z

MateoConLechuga at 09:19, 26 May 2016

2016-05-26T09:19:37Z

MateoConLechuga: /* Synopsis */

2016-05-26T09:16:59Z

‎Synopsis

MateoConLechuga: Created page with "003A - Stack Protector Stack Protector == Synopsis == '''Port Number:''' 003A-003C '''Function:''' Stack..."

2016-05-26T09:01:55Z

Created page with "003A - Stack Protector Stack Protector == Synopsis == '''Port Number:''' 003A-003C '''Function:''' Stack..."

New page

[[Category:84PCE:Ports:By_Address|003A - Stack Protector]] [[Category:84PCE:Ports:By_Name|Stack Protector]]
== Synopsis ==
'''Port Number:''' 003A-003C

'''Function:''' Stack Protector Ports

This range of ports holds the location of the bottom of the stack. When the the default address D19881 is written to, a non-maskable interrupt is generated which shuts down the calculator and clears all of RAM. This could potentially have uses such as a hardware breakpoint in z80 mode.

==Example==
Since the stack protector is extremely simple, this equally simple program will cause a crash.

ld (0D19881h),a
ret

@@ Line 5: / Line 5: @@
 '''Function:''' Stack Protector Ports
-This range of ports holds the location of the bottom of the stack. When the default address D19881 is written to, a non-maskable interrupt is generated which resets the calculator, clearing all of RAM. This could potentially have uses such as a hardware write breakpoint in z80 mode.
+This range of ports holds the location of the bottom of the stack (LSB in 3A, MSB in 3C). When the byte at this address (the OS sets it to D19881 by default) is written to, the write affects memory and a non-maskable interrupt is generated (regardless of whether the code is privileged) which resets the calculator, clearing all of RAM. This could potentially have uses such as a hardware write breakpoint in z80 mode.
 ==Example==

@@ Line 5: / Line 5: @@
 '''Function:''' Stack Protector Ports
-This range of ports holds the location of the bottom of the stack. When the the default address D19881 is written to, a non-maskable interrupt is generated which resets the calculator, clearing all of RAM. This could potentially have uses such as a hardware write breakpoint in z80 mode.
+This range of ports holds the location of the bottom of the stack. When the default address D19881 is written to, a non-maskable interrupt is generated which resets the calculator, clearing all of RAM. This could potentially have uses such as a hardware write breakpoint in z80 mode.
 ==Example==

@@ Line 5: / Line 5: @@
 '''Function:''' Stack Protector Ports
-This range of ports holds the location of the bottom of the stack. When the the default address D19881 is written to, a non-maskable interrupt is generated which resets the calculator, clearing all of RAM. This could potentially have uses such as a hardware breakpoint in z80 mode.
+This range of ports holds the location of the bottom of the stack. When the the default address D19881 is written to, a non-maskable interrupt is generated which resets the calculator, clearing all of RAM. This could potentially have uses such as a hardware write breakpoint in z80 mode.
 ==Example==