I haven't seen signed wires. You have to convert signed input [-128, 127] into the binary offset [0, 255] and work with unsigned wires.
Take a look on Sine/Cosine generator example posted by JLS1, particularly how higher bits are padded to make binary offset values:
Can you describe more about the input source and component functionality?
thank you, I'll look into it and check if I can solve my problem based on this.