MCU POCSAG code error detection and correction

*/ ***** POCSAG code error detection and correction ***** /*

*/ Operation result: Flag_Bits.VER_ER=0, the reception is correct or the error code has been corrected;
Flag_Bits.VER_ER=1, the reception is wrong and cannot be corrected;
Completely received codeword: Code_Reg/*

unsigned long Code_Reg; */Code_Reg: stores the recently received POCSAG codeword; /*

*/ Error pattern array for error correction/*
const unsigned int Err_s[]={0x3B4,0x1DA,0xED,0x3C2,0x1E1,0x344,0x1A2,0xD1,0x3DC,0x1EE,0xF7,

0x3CF,0x253,0x29D,0x2FA,0x17D,0x30A,0x185,0x376,0x1BB,0x369,0x200,

0x100,0x80,0x40,0x20,0x10,0x8,0x4,0x2,0x1};

struct Bits
{
POCSAG:1; */The value of the current bit of the received POCSAG code/*
VER_ER:1; */Error flag*/
}Flag_Bits;

void Rcv_POCSAG_Code(void)
{
unsigned char Count;
unsigned long Round_Reg;
unsigned int Ver_Reg;

Code_Reg=0;Ver_Reg=0;
for(Count=31;Count>0;Count--)
{
;
/*This contains the instruction to read one bit of the POCSAG code and store this bit in Flag_Bits.POCSAG*/
;
Code_Reg<<=1;Ver_Reg<<=1;
if(Flag_Bits.POCSAG){Code_Reg++;Ver_Reg++;}
if((Ver_Reg&0x400)>0)Ver_Reg^=0x769;
}
if(Ver_Reg>0)
{
Flag_Bits.VER_ER=1;Round_Reg=1;Count=31;
do
{
if(Ver_Reg==Err_s[--Count])
{
Code_Reg^=Round_Reg;
Flag_Bits.VER_ER=0;break;
}
Round_Reg<<=1;
}while(Count>0);
}
;
/*Read the last bit of the POCSAG code (parity check) and store it in Flag_Bits.POCSAG*/
;
Code_Reg<<=1;if(Flag_Bits.POCSAG){Code_Reg++;}
}

1. A careful colleague suggested that the error correction section should be modified as follows:

if(Ver_Reg==0)
{
Flag_Bits.VER_ER=0;
}
else
{
Flag_Bits.VER_ER=1;Round_Reg=1;Count=31;
;
;
}

His suggestion is good. After the modification, Flag_Bits.VER_ER can strictly reflect the result of verification or error correction. Colleagues should pay attention to it when quoting this program.
In fact, in the original program, "/*Here is an instruction to read one bit of POCSAG code and store this bit in Flag_Bits.POCSAG*/" includes a software filtering program. Flag_Bits.VER_ER is used here to reflect the success or failure of software filtering. If the software filtering cannot determine whether the current received signal is 0 or 1, Flag_Bits.VER_ER is set to 1 and immediately returns to the upper program. Therefore, Flag_Bits.VER_ER is cleared before executing verification and error correction. According
to the same characteristics of the BCH code error detection algorithm and the algorithm for generating the check code, the generation program of the POCSAG code check code can be slightly modified in this program (of course, the error correction part must be discarded), and I will not repeat it here.