Byte number definition
Byte number means all byte number from the byte(excluding the byte) to CRC byte(excluding the byte). 04 means there are 4 byte of data from the “byte number” to “CRC CHK low bit”, which are “digital address 0004H high bit”, “digital address 0004H low bit”, “digital address 0005H high bit” and “digital address 0005H low bit”.
Byte number means all byte number from the byte (excluding the byte) to CRC byte (excluding the byte). 04 means there are 4 byte of data from the "byte number" to "LSB of CRC CHK", which are "MSB of data in 0004H", "LSB of data in 0004H", "MSB of data in 0005H" and "LSB of data in 0005H".