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unit timer;
{ NOT PORTED YET, BUT NOT USED BY OTHER LIBS/AND OR DLL AND MOST DEMOES}
{$r-,s-}
INTERFACE
var
timeractive: boolean;
exacttime, mstime: longint;
function timervalue: longint; {Return time in 10 usec units}
function mstimer: longint; {Return time in ms}
IMPLEMENTATION
uses dos, crt;
var
lowbyte, highbyte, ref: word;
timerid: integer;
saveint, exitsave: pointer;
function inport(x: integer): byte; {Read i/o port}
inline($5a/$eb/$00/$ec);
{$F+}
procedure clock(p: pointer); interrupt;
{$F-}
{Interrupt service routine to update timer reference values}
const
incr = 5493; {Timer increment per interrupt}
begin
port[$43] := $00; {Latch timer 0}
lowbyte := inport($40);
highbyte := inport($40);
ref := (highbyte shl 8) + lowbyte; {Base for subsequent readings
within current clock interval}
exacttime := exacttime + incr; {New 10 usec timer value}
mstime := mstime + 55; {New ms timer value}
inline($9c/$ff/$1e/saveint); {Chain to old interrupt}
end;
function timervalue: longint;
{Get value of 10-usec timer}
var
dif, low, high: word;
t: longint;
begin
inline($fa); {Disable interrupts}
port[$43] := $00; {Latch timer}
low := inport($40); {Timer LSB}
high := inport($40); {MSB}
dif := ref - ((high shl 8) + low); {Delta from last sync}
timervalue := exacttime + (longint(dif)*100 div 1193);
inline($fb); {Re-enable interrupts}
end;
function mstimer: longint;
{Get value of millisecond timer}
var
dif, low, high: word;
t: longint;
begin
inline($fa);
port[$43] := $00;
low := inport($40);
high := inport($40);
inline($fb);
dif := ref - ((high shl 8) + low);
mstimer := mstime + (dif div 1193);
end;
procedure inittimer;
begin
exacttime := 0;
mstime := 0;
if not timeractive then
begin
port[$43] := $34; {Mode 2 - countdown
(approx .84 microsecond ticks)}
port[$40] := $ff; {Initialize timer value}
port[$40] := $ff;
getintvec(8, saveint); {Save old interrupt address}
setintvec(8, @clock); {Install new service routine}
timeractive := true;
delay(60); {Allow for first tick}
end;
end;
{$f+} procedure myexit; {$f-}
{Assure timer interrupt restored before exit}
begin
if timeractive then
setintvec(8, saveint);
exitproc := exitsave; {Restore TP exit chain}
end;
begin {unit initialization}
timeractive := false;
exitsave := exitproc; {Insert exit routine}
exitproc := @myexit;
InitTimer
end.
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