242 lines
8.7 KiB
NASM
242 lines
8.7 KiB
NASM
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; Command & Conquer Red Alert(tm)
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; Copyright 2025 Electronic Arts Inc.
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;
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; This program is free software: you can redistribute it and/or modify
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; it under the terms of the GNU General Public License as published by
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; the Free Software Foundation, either version 3 of the License, or
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; (at your option) any later version.
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;
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; This program is distributed in the hope that it will be useful,
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; but WITHOUT ANY WARRANTY; without even the implied warranty of
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; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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; GNU General Public License for more details.
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;
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; You should have received a copy of the GNU General Public License
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; along with this program. If not, see <http://www.gnu.org/licenses/>.
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;
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;***************************************************************************
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;** C O N F I D E N T I A L --- W E S T W O O D S T U D I O S **
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;***************************************************************************
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;* *
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;* Project Name : Timer interrupt for RM *
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;* *
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;* File Name : TIMEREAL.ASM *
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;* *
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;* Programmer : Scott K. Bowen *
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;* *
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;* Start Date : July 8, 1994 *
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;* *
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;* Last Update : July 8, 1994 [SKB] *
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;* *
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;*-------------------------------------------------------------------------*
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;* Functions: *
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;* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - *
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IDEAL
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MODEL TINY
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P386N
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LOCALS ??
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;//////////////////////////////////////////////////////////////////////////////////////
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;///////////////////////////////////// Equates ////////////////////////////////////////
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INTCHIP0 EQU 20h ; 8259 interrupt chip controller 0
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CLEARISR EQU 20h ; Value to write to 8259 to reenable interrupts.
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CODESEG
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;//////////////////////////////////////////////////////////////////////////////////////
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;///////////////////////////////////// Data ////////////////////////////////////////
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; This information may not change unless the protected mode version is
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; also changed.
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; For speed, PM uses a DD while RM used DW
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TrueRate DW 0 ; True rate of clock. (only use word)
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TrueRateNA DW 0 ; used for speed in prot mode.
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; For speed, SysRate and SysError are DD in PM and are DW in real mode.
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SysTicks DD 0 ; Tick count of timer.
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SysRate DD 0 ; Desired rate of timer.
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SysError DD 0 ; Amount of error in clock rate for desired frequency.
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SysCurRate DW 0 ; Keeps track of when to increment timer.
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SysCurError DW 0 ; Keeps track of amount of error in timer.
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UserTicks DD 0 ; Tick count of timer.
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UserRate DD 0 ; Desired rate of timer.
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UserError DD 0 ; Amount of error in clock rate for desired frequency.
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UserCurRate DW 0 ; Keeps track of when to increment timer.
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UserCurError DW 0 ; Keeps track of amount of error in timer.
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DosAdder DW 0 ; amount to add to DosFraction each interrupt.
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DosFraction DW 0 ; Call dos when overflowed.
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OldRMI DD 0 ; The origianl RM interrupt seg:off.
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OldPMIOffset DD 0 ; The origianl PM interrupt offset
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OldPMISelector DD 0 ; The original PM interrupt segment.
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CodeOffset DW RM_Timer_Interrupt_Handler ; Offset of the code in the RM stuff.
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CallRMIntOffset DW Call_Interrupt_Chain ; Offset of function to call DOS timer interrupt.
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CallRMIntAddr DD 0 ; PM address of CallRealIntOffset for speed.
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PMIssuedInt DD 0 ; PM signals RM to just call Int chain.
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; These are just used for information on testing. When all is done, they can
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; be removed, but why? The don't add too much proccessing time and can
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; be useful.
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NumPMInts DD 0 ; Number of PM interrupts
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NumRMInts DD 0 ; Number of RM interrupts.
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;//////////////////////////////////////////////////////////////////////////////////////
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;///////////////////////////////////// Code ////////////////////////////////////////
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; This is here for easy comparison with the PM version.
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MACRO INCREMENT_TIMERS
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inc [NumRMInts] ; For testing.
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; At this point, increment the system and user timers.
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mov ax,[TrueRate] ; Get the rate of the PC clock.
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sub [SysCurRate],ax ; Sub from our rate counter.
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ja ??end_sys ; If !below zero, do not inc.
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mov bx,[WORD PTR SysRate] ; Get rate of timer.
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mov dx,[WORD PTR SysError] ; Get amount of error.
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add [SysCurRate],bx ; Add rate to the current.
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sub [SysCurError],dx ; Subtract err from error count.
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jb ??error_adj_sys ; If !below 0, increment counter.
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inc [SysTicks] ; increment the timer.
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jmp short ??end_sys ; don't modify SysCurError.
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??error_adj_sys:
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add [SysCurError],bx ; reajust the error by timer rate.
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??end_sys:
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sub [UserCurRate],ax ; Sub from our rate counter.
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ja ??end_user ; If !below zero, do not inc.
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mov bx,[WORD PTR UserRate] ; Get rate of timer.
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mov dx,[WORD PTR UserError] ; Get amount of error.
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add [UserCurRate],bx ; Add rate to the current.
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sub [UserCurError],dx ; Subtract err from error count.
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jb ??error_adj_user ; If !below 0, increment counter.
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inc [UserTicks] ; increment the timer.
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jmp short ??end_user ; don't modify UserCurError.
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??error_adj_user:
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add [UserCurError],bx ; reajust the error by timer rate.
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??end_user:
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ENDM
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;**************************************************************************
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;* RM_INTERRUPT_HANDLER -- Called when processor interrupted in real mode. *
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;* *
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;* *
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;* INPUT: *
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;* *
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;* OUTPUT: *
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;* *
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;* WARNINGS: *
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;* *
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;* HISTORY: *
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;* 07/08/1994 SKB : Created. *
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;*=========================================================================*
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label RM_Timer_Interrupt_Handler
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start_RM_Timer_Interrupt_Handler:
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push ax
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push bx
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push dx
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push ds
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mov ax,cs ; Set data segment to code segment
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mov ds,ax ; since data is in code seg.
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cmp [WORD PTR PMIssuedInt],0; Check to see if PM made Int call.
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mov [WORD PTR PMIssuedInt],0; Make it false.
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jne ??call_int_chain ; if so, just call Int Chain.
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INCREMENT_TIMERS
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; Now check to see if we should call the old timer handler.
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mov ax,[DosAdder] ; Get amount to add each tick.
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add [DosFraction],ax ; add it to the fraction.
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jnc ??no_int_chain ; Skip call if no overflow.
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??call_int_chain:
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pushf ; Push flags for interrupt call.
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call [OldRMI] ; chain the call.
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??no_int_chain:
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sti
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mov al,CLEARISR ; value to clear In Service Register
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mov dx,INTCHIP0
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out dx,al ; 8259 interrupt chip controller 0
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exit1:
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pop ds
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pop dx
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pop bx
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pop ax
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iret
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;**************************************************************************
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;* CALL_INTERRUPT_CHAIN -- Function PM calls to call the RM interrupt chain*
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;* *
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;* *
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;* INPUT: *
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;* *
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;* OUTPUT: *
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;* *
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;* WARNINGS: *
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;* *
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;* HISTORY: *
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;* 07/08/1994 SKB : Created. *
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;*=========================================================================*
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Call_Interrupt_Chain:
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pushf
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call [OldRMI] ;
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retf
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STACK ; Don't really need this
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END
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IF 0
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; mono print stuff.
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pushf
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push ax
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push di
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push es
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mov ax,0B000h ; ES:DI = Mono RAM address.
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mov es,ax
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mov al,'A'
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mov ah,2
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and di,63
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stosw
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pop es
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pop di
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pop ax
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popf
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ENDIF
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