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emm08_a.asm
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Assembly Source File
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1989-11-29
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6KB
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104 lines
;-----------------------------------------------------------------------------;
; MODULE NAME: EMM08_A.ASM ;
; ;
; FUNCTION NAME: save_context ;
; ;
; DESCRIPTION: This function saves the contents of the page mapping ;
; hardware on all expanded memory boards. (The contents ;
; are saved in a memory manager internal save area.) ;
; The function is typically used to save the memory ;
; mapping context of the EMM handle that was active when ;
; a software or hardware interrupt occurred. (See ;
; restore_context for the restore operation.) ;
; ;
; If you're writing a resident program, an interrupt ;
; service routine, or a device driver that uses expanded ;
; memory, you must save the state of the mapping ;
; hardware. You must save this state because application ;
; software using expanded memory may be running when your ;
; program is invoked by a hardware interrupt, a software ;
; interrupt, or DOS. ;
; ;
; The save_context function requires the EMM handle that ;
; was assigned to your resident program, interrupt ;
; service routine, or device driver at the time it was ;
; initialized. This is not the EMM handle that the ;
; application software was using when your software ;
; interrupted it. ;
; ;
; The save_context function saves the state of the map ;
; hardware for only the 64K-byte page frame defined in ;
; versions 3.x of this specification. Since all ;
; applications written to LIM versions 3.x require saving ;
; the map hardware state of only this 64K-byte page ;
; frame, saving the entire mapping state for a large ;
; number of mappable pages would be inefficient use of ;
; memory. Applications that use a mappable memory region ;
; outside the LIM 3.x page frame should use the ;
; get_context, set_context, get_set_context, ;
; get_partial_context, set_partial_context functions to ;
; save and restore the state of the map hardware. ;
; ;
; PASSED: handle: ;
; is the EMM handle assigned to the interrupt service ;
; routine that's servicing the software or hardware ;
; interrupt. The interrupt service routine needs to ;
; save the state of the page mapping hardware before ;
; mapping any pages. ;
; ;
; RETURNED: status: ;
; is the status EMM returns from the call. All other ;
; returned results are valid only if the status ;
; returned is zero. Otherwise they are undefined. ;
; ;
; C USE CONVENTION: unsigned int status; ;
; unsigned int handle; ;
; ;
; status = save_context (handle); ;
;-----------------------------------------------------------------------------;
.XLIST
PAGE 60,132
IFDEF SMALL
.MODEL SMALL, C
ENDIF
IFDEF MEDIUM
.MODEL MEDIUM, C
ENDIF
IFDEF LARGE
.MODEL LARGE, C
ENDIF
IFDEF COMPACT
.MODEL COMPACT, C
ENDIF
IFDEF HUGE
.MODEL HUGE, C
ENDIF
INCLUDE emmlib.equ
INCLUDE emmlib.str
INCLUDE emmlib.mac
.LIST
.CODE
save_context PROC \
handle:WORD
;---------------------------------------------------------------------;
; do; ;
; . save the LIM 3.X mapping context within EMM; ;
;---------------------------------------------------------------------;
MOVE AH, save_page_map_fcn
MOVE DX, handle
INT EMM_int
;---------------------------------------------------------------------;
; . return (EMM status); ;
; end; ;
;---------------------------------------------------------------------;
RET_EMM_STAT AH
save_context ENDP
END