JVC rs-840UD owner manual Controlling the Multiple Product, RS-232C RJ-45, RS232C CheckSum, 1byte

RS-232C RJ-45

Controlling the Multiple Product

		Header (5 bytes)					Payload (4 bytes)			Checksum
										(1byte)
	Prefix code	Prefix code	Set	Payload	# of
command					payload	Command	data #0	data #1	data #2	CS #0
	#0	#1	ID	Type
					bytes
Ack Set Wide	0xCC	0x55		0	4	0xC2	0xE0 : OK	reserved (0xFF)	reserved	Header XOR
Mode							0xE1 : NG		(0xFF)	Payload
Read Wide	0xCC	0x33		1	4	0xC2	reserved (0x00)	reserved (0x00)	reserved	Header XOR
Mode									(0x00)	Payload
Ack Read	0xCC	0x55		1	4	0xC2	0xE0 : OK	0 : Normal/Full	reserved	Header XOR
Wide Mode							0xE1 : NG	1 : Wide	(0x00)	Payload
								2 : Zoom
								3 : Stretch/
								Panoramic
Set Video	0xCC	0x33		0	4	0xCC	0 : 60Hz	reserved (0xFF)	reserved	Header XOR
System							1 : 50Hz		(0xFF)	Payload
Ack Set Video	0xCC	0x55		0	4	0xCC	0xE0 : OK	reserved (0xFF)	reserved	Header XOR
System							0xE1 : NG		(0xFF)	Payload
Read Video	0xCC	0x33		1	4	0xCC	reserved (0x00)	reserved (0x00)	reserved	Header XOR
System									(0x00)	Payload
Ack Read	0xCC	0x55		1	4	0xCC	0xE0 : OK	0 : 60Hz	reserved	Header XOR
Video System							0xE1 : NG	1 : 50Hz	(0xFF)	Payload

RS232C CheckSum
		Header (5 bytes)					Payload (4 bytes)			Checksum
										(1byte)
command	Prefix code	Prefix code	Set	Payload	# of payload	Command	data #0	data #1	data #2	CS #0
	#0	#1	ID	Type	bytes
Set Power	0xCC	0x33		0	4	0x10	"0 : 0ff	reserved	reserved	Header XOR
							1 : On"	(0x00)	(0x00)	Payload

We can make CheckSum with Header (5 bytes) and Payload(4 bytes).

(Prefix code#0) XOR (Prefix code#1) XOR (Set ID) XOR (Command Payload Type) XOR (# of Payload bytes) XOR (Command) XOR (data #0) XOR (data #1) XOR (data#2) = CheckSum

For example:

(0xCC) XOR (0x33) XOR (0x01 = Set ID) XOR (0x00) XOR (0x04) XOR (0x10) XOR (0x01 = ON) XOR (0x00) XOR (0x00) = 0xEB

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