C数组值有时会被否定

I am trying to put an integer value into a character array so I can have byte addressable memory. When I pass the integer I want to place and the character pointer to the array into my function they have the correct values. After the assignment the integer pointer keeps the correct value but the character pointer has the negative value. This only happens two times out of ten and on the same two numbers every time.. Here is a snippet of the functionI am trying to put an integer value into a char