Hi New to RS232 and I have a quick question ( I Hope )

I have a Denon BRP 2010 and I want to control it with an RTI T2C using RS232 strings I have obtained the 232 protocol from Denon and I can see how to Obtain the first 16 Digits but the last 4 have stumped me BCCH BCCL (Block Check Character High Byte and Low Byte) as I understand it, can anyone help on this one

Thanks

Basil