mirror of https://github.com/saitohirga/WSJT-X.git
26 lines
665 B
Fortran
26 lines
665 B
Fortran
subroutine get_crc24(mc,len,ncrc)
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!
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! 1. To calculate 24-bit CRC, mc(1:len-24) is the message and mc(len-23:len) are zero.
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! 2. To check a received CRC, mc(1:len) is the received message plus CRC.
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! ncrc will be zero if the received message/CRC are consistent.
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!
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character c24*24
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integer*1 mc(len)
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integer*1 r(25),p(25)
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integer ncrc
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! polynomial for 24-bit CRC 0x100065b
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data p/1,0,0,0,0,0,0,0,0,0,0,0,0,0,1,1,0,0,1,0,1,1,0,1,1/
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! divide by polynomial
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r=mc(1:25)
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do i=0,len-25
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r(25)=mc(i+25)
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r=mod(r+r(1)*p,2)
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r=cshift(r,1)
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enddo
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write(c24,'(24b1)') r(1:24)
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read(c24,'(b24.24)') ncrc
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end subroutine get_crc24
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