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Chapter 5
//Set the value of CRT2 as 65,535 for down counting
outport(addr2_1712+0x24,0x80);
outport(addr2_1712+0x24,0x88);
outport(addr2_1712+0x24,0x00);
outport(addr2_1712+0x24,0x52);
outport(addr2_1712+0x22,0x80);
outport(addr2_1712+0x22,0x88);
outport(addr2_1712+0x22,0x80);
outport(addr2_1712+0x22,0x81);
//Check if CNT2's gate and clock are in logic-high status
//It means that if frequency measurement is in progress
while(i != 0x500)
{
}
//The CNT2 has started to do frequency measurement
//Check if CNT2's gate is in logic-low status
//It checks if frequency measurementis over?
while(1)
{
}
/*The CNT2 has finished the job, and then show the measured
frequency on display*/
dl= inport(addr2_1712+0x1c);
dh= inport(addr2_1712+0x1c)<<8;
dh= dh + (dl & 0x00ff);
old_count = 0xffff - dh ;
PCI-1712/1712L User's Manual
i = inport(addr2_1712+0x24) & 0x0500 ;
i = inport(addr2_1712+0x24) & 0x0100 ;
if(i!=0x0100) break;
– 50 –
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//Set CNT2's gate input as high
/*Generate one clock to CNT2,
and set CNT2's gate input as
low*/
/*Set CNT2's clock source as
external from CNT1's OUT, and
negative polarity*/
//Set CNT1's gate input as high
//Generate one clock to CNT1
//Set CNT1's clk source as
//internal
//Read low byte
//Read high byte
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