WSJT-X/lib/ft8/get_crc14.f90

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subroutine get_crc14(mc,len,ncrc)
!
! 1. To calculate 14-bit CRC, mc(1:len-14) is the message and mc(len-13:len) are zero.
! 2. To check a received CRC, mc(1:len is the received message plus CRC.
! ncrc will be zero if the received message/CRC are consistent
!
character c14*14
integer*1 mc(len)
integer*1 r(15),p(15)
integer ncrc
! polynomial for 14-bit CRC 0x6757
data p/1,1,0,0,1,1,1,0,1,0,1,0,1,1,1/
! divide by polynomial
r=mc(1:15)
do i=0,len-15
r(15)=mc(i+15)
r=mod(r+r(1)*p,2)
r=cshift(r,1)
enddo
write(c14,'(14b1)') r(1:14)
read(c14,'(b14.14)') ncrc
end subroutine get_crc14