Kramer Electronics 7508 user manual Communication Protocol, Structure of the Protocol

Communication Protocol

7 Communication Protocol

RS-232 communication with the 7508 complies with the following protocol. The protocol uses 4 bytes of information, and data is at 9600 baud, with no parity, 8 data bits and 1 stop bit.

Table 4: Structure of the Protocol

MSB											LSB
							INSTRUCTION
0	TO PC		I5	I4		I3		I2	I1		I0
7	6		5	4		3		2	1	0
1st byte
							DATA
1	D6		D5	D4		D3		D2	D1		D0
7	6		5	4		3		2	1	0
2nd byte
					EXTENDED DATA
1	E6		E5	E4		E3		E2	E1		E0
7	6		5	4		3		2	1	0
3rd byte
		MSB’s									ADDR
1	E7		D7	0		0		1	1		0
7	6		5	4		3		2	1		0
4th byte1

Note that the MSB’s of the DATA (D7) and the EXTENDED DATA (E7) are in the fourth byte.

Terminology:

•TO PC is the “DESTINATION BIT”

•I4..I0 is the “INSTRUCTION”

•D7..D0 is the “DATA”

•E7..E0 is the “EXTENDED DATA”

•A0 is the “LSB of the MACHINE ADDRESS”

The destination bit, TO PC, is 0 when sending from the PC to the machine, or 1 when sending from the machine to the PC.

Table 5: Instruction Set for the 7508

#	INSTRUCTION	I5	I4	I3	I2	I1	I0
0	Reset	0	0	0	0	0	0
1	Read video standard	0	0	0	0	0	1
3	Read back-panel DIP-switch 1 (video format CV/YC)	0	0	0	0	1	1
10	Write EEPROM data – low address	0	0	1	0	1	0
11	Read EEPROM data – low address	0	0	1	0	1	1
12	Write I²C	0	0	1	1	0	0
13	Read I²C	0	0	1	1	0	1
16	Error	0	1	0	0	0	0
57	Enable “Power-down save”	1	1	1	0	0	1
61	Identify machine	1	1	1	1	0	1

1 Note that the MSB’s of the DATA (D7) and the EXTENDED DATA (E7) are in the fourth byte

10 KRAMER: SIMPLE CREATIVE TECHNOLOGY