Intel Microcontroller, 80C196NU manual Unsupported Locations Windowing Example 8XC196NP Only

MEMORY PARTITIONS

5.3.2.4Unsupported Locations Windowing Example (8XC196NP Only)

Assume that you wish to access location 1FE7H (the EP_PIN register, a memory-mapped SFR) with direct addressing through a 128-byte window. This location is in the range of addresses (1FE0–1FFFH) that cannot be windowed. Although you could set up the window by writing 1FH to the WSR, reading this location through the window would return FFH (all ones) and writing to it would not change the contents. However, you could directly address the remaining SFRs in the range of 1F80–1FDFH.

5.3.2.5Using the Linker Locator to Set Up a Window

In this example, the linker locator is used to set up a window. The linker locator locates the win- dow in the upper register file and determines the value to load in the WSR for access to that win- dow. (Please consult the manual provided with the linker locator for details.)

*********			mod1	**************
mod1	module main				;Main module for linker
public function1
extrn	?WSR				;Must declare ?WSR as external
wsr	equ		14h:byte
sp	equ		18h:word
oseg
	var1:		dsw	1	;Allocate variables in an overlayable segment
	var2:		dsw	1
	var3:		dsw	1
cseg
function1:
	push		wsr		;Prolog code for wsr
	ldb		wsr, #?WSR		;Prolog code for wsr
	add	var1, var2, var3			;Use the variables as registers
	;
	;
	;
	ldb		wsr, [sp]		;Epilog code for wsr
	add	sp, #2			;Epilog code for wsr
	ret
end
********			mod2	**************

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