1. X-10 Transmission Coding (overview).

1.1 Housecodes and Device Codes.

The housecodes and device codes range from A to P and 1 to 16 respectively although they do not follow a binary sequence. The encoding format for these codes is as follows

	Housecode	Device Code	Binary Value
	A		1		0110
	B		2		1110
	C		3		0010
	D		4		1010
	E		5		0001
	F		6		1001
	G		7		0101
	H		8		1101
	I		9		0111
	J		10		1111
	K		11		0011
	L		12		1011
	M		13		0000
	N		14		1000
	O		15		0100
	P		16		1100

1.2 Function Codes.

	Function			Binary Value
	All Units Off			0000
	All Lights On			0001
	On				0010
	Off				0011
	Dim				0100
	Bright				0101
	All Lights Off			0110
	Extended Code			0111
	Hail Request			1000
	Hail Acknowledge		1001
	Pre-set Dim (1)			1010
	Pre-set Dim (2)			1011
	Extended Data Transfer		1100
	Status On			1101	
	Status Off			1110
	Status Request			1111

NOTE: The only devices that I own that respond to the status request command are the RR501 RF receivers. If anyone knows of others I'd like to hear about them.

2. Serial Parameters.

The serial parameters for communications between the interface and PC are as follows:

	Baud Rate:	4,800bps
	Parity:		None
	Data Bits:	8
	Stop Bits:	1

2.1 Cable connections:

        Signal  DB9 Connector   RJ11 Connector
        SIN     Pin 2           Pin 1
        SOUT    Pin 3           Pin 3
        GND     Pin 5           Pin 4
        RI      Pin 9           Pin 2

where:  SIN     Serial input to PC (output from the interface)
        SOUT    Serial output from PC (input to the interface)
        GND     Signal ground
        RI      Ring signal (input to PC)

3. X-10 Transmission.

3.1. Standard Transmission.

An X-10 transmission from the PC to the interface typically refers to the communication of a Housecode and Device Code combination or the transmission of a function code. The format of these transmissions is:

		PC			Interface
2 bytes		Header:Code
1 byte					checksum
1 byte		Acknowledge
1 byte					interface ready to receive

This format is typical of all transmissions between the PC and the interface with the difference being in the first transmission from the PC.

3.1.1. Header:Code.

The Header:Code combination is configured thus:



Header:Code

BIT:	7	6	5	4	3	2	1	0
Header:	Dim Amount					1	F/A	E/S


Where:
Dim amount (dims) is a value between 0 and 22 identifying the number of dims to be transmitted (22 is equivalent to 100%)
Bit 2 is always set to '1' to ensure that the interface is able to maintain synchronization.
F/A defines whether the following byte is a function (1) or address (0).
E/S defines whether the following byte is an extended transmission (1) or a standard transmission (0).



Header:Code

BIT:	7	6	5	4	3	2	1	0
Address:	Housecode				Device Code
Function:	Housecode				Function


Note the function only operates for devices addressed with the same Housecode.

3.1.2. Interface Checksum and PC Acknowledge

When the interface receives a transmission from the PC, it will sum all of the bytes, and then return a byte checksum. If the checksum is correct, the PC should return a value of 0x00 to indicate that the transmission should take place. If however, the checksum is incorrect, then the PC should again attempt to transmit the Header:Code combination and await a new checksum.

3.1.3. Interface Ready to Receive.

Once the X-10 transmission has taken place (and this may be quite time consuming in the case of Dim or Bright commands) the interface will send 0x55 to the PC to indicate that it is in a 'ready' state.

3.1.4. Example.

	PC		Interface	Description
	0x04,0x66			Address A1
			0x6a		Checksum ((0x04 + 0x66)&0xff)
	0x00				OK for transmission.
			0x55		Interface ready.

	0x04,0x6e			Address A2
			0x72		Checksum ((0x04 + 0x6e)&0xff)
	0x00				OK for transmission.
			0x55		Interface ready.

	0x86,0x64			Function: A Dim 16/22*100%
			0xe0		Incorrect checksum.
	0x86,0x64			Function re-transmission
			0xea		Checksum ((0x86 + 0x64)&0xff)
	0x00				OK for transmission.
			0x55		Interface ready.

This transmission will address lamp modules A1 and A2, and then dim them by 72%. Note multiple addresses cannot be made across housecodes, i.e. A1, B2 Dim 72% is not valid, and would result in B2 being dimmed by 72%.

3.2. Extended X-10 Transmission.

Extended X-10 transmission is simply an extension of the protocol to allow two additional bytes of extended data to be transmitted. In this case, the protocol may be shown as:

		PC			Interface
4 bytes		Header:Code:Data:Command
1 byte					checksum
1 byte		Acknowledge
1 byte					interface ready to receive

The header for an extended transmission is always:

	Bits:	7   6   5   4   3   2   1   0
	Header:	0   0   0   0   0   1   1   1

Bits 7 to 3 are always zero because the dim level is not applicable to extended transmissions.
Bit 2 must be set to '1' as in all PC header transmissions.
Bit 1 is set to '1' as the extended transmission is always a function.
Bit 0 is set to '1' to define an extended transmission rather than a standard transmission.
The function byte is:

	Bits:      7   6   5   4   3   2   1   0
	Function:  < Housecode >   0   1   1   1

Again, the housecode must be the same as any previously addressed modules, and for extended data, the function code must be 0111. Finally, the data and command bytes may take any value between 0x00 and 0xff. Note that the checksum is one byte and is defined as:

	checksum = (header + code + data + command)&0xff

4. X-10 Reception.

Whenever the interface begins to receive data from the power-line, it will immediately assert the serial ring (RI) signal to initiate the wake-up procedure for the PC. Once the data reception is complete, the interface will begin to poll the PC to upload its data buffer (maximum 10 bytes). If the PC does not respond, then the interface's data buffer will overrun, and additional data will not be stored within the buffer.

4.1. Interface Poll Signal.

In order to poll the PC, the interface will continually send:

	bits:	7   6   5   4   3   2   1   0
	Poll:	0   1   0   1   1   0   1   0		(0x5a)

This signal will be repeated once every second until the PC responds.

4.2. PC Response to the Poll Signal.

To terminate the interface's polling and initiate the data transfer, the PC must send an acknowledgment to the interface's poll signal. This acknowledgment is: bits: 7 6 5 4 3 2 1 0 Ack : 1 1 0 0 0 0 1 1 (0xc3) Notice that bit #2 of the PC transmission is not set, indicating that this cannot be the beginning of a transmission from the PC.

4.3. Interface Serial Data Buffer.

The buffer consists of 10 bytes defined as follows: Byte Function 0 Upload Buffer Size 1 Function / Address Mask 2 Data Byte #0 3 Data Byte #1 4 Data Byte #2 5 Data Byte #3 6 Data Byte #4 7 Data Byte #5 8 Data Byte #6 9 Data Byte #7 The interface will only upload the specified number of bytes within the buffer, and will not default to uploading 10 bytes in every transmission. The number of bytes to receive is thus specified in byte 0 of the transmission. The counting of the number of bytes starts at the mask (shown as byte 1). The function address mask indicates whether the following 8 bytes should be interpreted as an address or as a function. The position of the bit in the mask corresponds to the Data byte index within the data buffer. If the bit is set (1), the data byte is defined as a function, and if reset (0), the byte is an address. Bit 0 coresponds to Data Byte 0. The data bytes are in the same format as for the Code byte in the X-10 transmissions (i.e. Housecode:Device Code or Housecode:Function). Note that once the data buffer has been uploaded, there is no acknowledgment from the PC to the interface as the contents of the serial data buffer will have been changed. This will not cause a problem as this is simply informing the PC of the external status, rather than controlling a device (as in the case of the PC transmission) which may have safety implications.

4.4. Dim or Bright.

After a dim or bright code, the PC will expect the following byte to be the change in brightness level. An X-10 module has 210 discrete brightness levels, and therefore this byte will be equivalent to a brightness change of n/210*100%.

4.5. Extended Code.

Extended code is processed in a similar way to Dim and Bright, except that the PC will expect two bytes, which are the Data and Command bytes.

4.6. Example.

PC Interface Description 0x5a Poll from interface. 0xc3 'PC Ready' Response from PC 0x06 6 byte transmission 0x04 xxxx x100-> byte 0,1 addresses, 2 function 0xe9 B6 0xe5 B7 0xe5 B Bright 0x58 0x58/210 * 100% This transmission will wake the computer, and then indicate that a transmission of length 5 bytes will occur, data bytes 0 and 1 are addresses and byte 2 is a bright function, which means that the following byte is the change in brightness level.

5. Fast Macro Download.

The interface contains a 42 byte buffer which contains macro codes. These macro codes are initiated upon the reception of a pre-defined address (i.e. B7), and the code specifies the transmissions that the interface should then make. Due to the shortage of bytes, the macro code is 'compressed' by grouping similar functions. Note, any error in the function codes may result in the interface entering an endless loop and becoming 'locked-up', so steps should be taken to ensure that the code is correct prior to transmission. If the interface detects that it has suffered a power-down situation, it will ring the PC and poll with a specialized code to indicate that the macros must be refreshed.

5.1. Power-fail Macro Download Poll Code.

NOTE: I beleive that this is mainly for the CP10. The battery backed CM11 does send this poll after a power failure, but it responds to a setclock directive rather than the macro download. It waits till the resumption of power before it starts sending this byte. DBS, Jan 1, 1997 In order to poll the PC, the interface will continually send: Poll: 7 6 5 4 3 2 1 0 Value: 1 0 1 0 0 1 0 1 (0xa5) This signal will be repeated once every second until the PC responds with a clock update ( 0x9b see section 8).

5.2. PC Response to Macro Download Poll Code.

To stop the polling, the PC must respond with: PC Response: 7 6 5 4 3 2 1 0 Value : 1 1 1 1 1 0 1 1 (0xfb) Once this has been transmitted, the macro must be immediately downloaded. At this stage, the interface will wait until the 42 byte macro has been received before any X-10 transmissions can occur.

5.3. Macro Code (CM10).

Macro code is divided into individual macros, and functional groups within the macros. The only limit to the number of macros and groups is the number of available storage bytes. Each macro begins with an initiator byte which details the Housecode and Device code that will cause the macro to start. Following the initiator byte is the length of this current macro, and the functional trigger (ie On or Off functions). The length is defined by the lower 7 bits, and the functional trigger by the most significant bit. If the most significant bit is set, the functional trigger is 'On', and if reset, the functional trigger is 'Off'. As mentioned previously, the macro is divided into functional groups, and each group has a byte indicating the length of the group before the macro is defined. This group length byte is exclusive of the function code. The group is then made up of a common housecode (1 nibble), followed by a number of device codes (each takes 1 nibble) and finally a function code (1 nibble). If the function code falls on a byte boundary, then it is always the low nibble of the byte. All unused bytes must take a value of 0x00.

5.3.1. Dimming and Brightening within a macro.

If the function is a bright or dim, then the next byte specifies the change in brightness level in 22 steps. Note if the most significant bit of this byte is set, the interface will send out enough bright commands to ensure that the associated lamps are at 100%, and then dim the lamp by the specified value.

5.3.2. Extended codes in macros.

Extended code cannot be grouped as for other functions, and consequently an extended code group would be defined as: Byte Description 0x01 Group length 0xa7 Housecode D (1010 = D), Extended code function 0x03 Device code 11 (0011 = 11) 0xff Data byte: 0xff 0x55 Command byte: 0x55

5.3.3. Checksum.

Once the macro has been downloaded, the interface calculates the 1 byte checksum by summing all 42 bytes of the macro code (not including the PC macro download start byte) and returns the appropriate value. If the value is incorrect, the PC should again initiate the macro download by transmitting the PC macro download start byte.

5.3.4. Example.

PC Interface Description 0xa5 Power-fail, macro poll. 0xfb Macro download start byte 0x26 Initiator C1 0x0a Functional Trigger: 'Off'; Macro length: 10 bytes 0x04 Group length: 4 nibbles 0x66 Macro housecode, A, device 1 0x2e Devices 2 and 3 0x04 Dim 0x0b Dim by 11/22*100% = 50% 0x02 group length: 2 nibbles 0x6a Macro housecode, A, device 4 0x02 Function: On 0x26 Initiator C1 0x8c Functional Trigger: 'On'; Macro length: 12 bytes 0x02 Group length: 2 nibbles 0x66 Macro housecode, A, device 1 0x02 Function: On 0x03 Group length: 3 nibbles 0x6e Macro housecode, A, device 2 0x42 Device 3, Function Dim (0100) 0x06 Dim by 6/22*100% = 27% 0x02 Group length: 2 nibbles 0x6a Macro housecode, A, device 4 0x03 Function: Off 0x00... Remaining 20 bytes set to 0x00 0x91 Macro checksum: 0x91 0x00 Checksum correct 0x55 Interface ready

5.4. EEPROM Code (CM11 and CP10).

The EEPROM code for the CM11 and CP10 contains both the downloaded timers and also the macro data. The timers are resolved into 'pseudo- macros' with the only difference being in the initiator (ie a timer as opposed to a macro code). In other words, a timer points to a macro. The timer initiator table is checked every minute to see if any of the entrys should trigger a macro. Macro initiators, on the other hand, are checked anytime an X10 signal is detected over the power lines. The EEPROM may be broken down into four categories: Macro Offset (two bytes) Timer Initiators (continues until an 0xff byte) Macro Initiators (continues to start of macro offset) Macro Data.

5.4.1. Macro Offset.

The first two bytes of the EEPROM contain an offset to the macro initiator table. The macro initiator table is offset rather than the timers as the timers must be processed every minute, whereas the macros are only processed whenever an X-10 transmission event is detected.

5.4.2. Timer Initiator.

The timers reside from address 0x0002 in the EEPROM and are delimited by a 0xff at the end of the table. Each timer entry contains the following data: Bit range Description 71 Reserved 70 to 64 Day of the week mask (bit 1 = Sunday, bit 7 = Saturday) 63 to 56 Start day range (day of the year) bits 0 to 7) 55 to 48 Stop day range (bits 0 to 7) 47 to 44 Event start time x 120 minutes 43 to 40 Event stop time x 120 minutes 39 Start day range (bit 8) 38 to 32 Event start time (0 to 120 minutes, bits 0 to 6) 31 Stop day range (bit 8) 30 to 24 Event stop time (0 to 120 minutes, bits 0 to 6) 23 to 20 Start event macro pointer (bits 8 to 11) 19 to 16 Stop event macro pointer (bits 8 to 11) 15 to 8 Start event macro pointer (bits 0 to 7) 7 to 0 Stop event macro pointer (bits 0 to 7) The day of the week and day of the year are anded, so both have to match the current time before the event will trigger a macro. The event macro pointer has the address of the macro that will be executed when this event is triggered.

5.4.3. Macro Initiator.

The macro initiators are configured thus: Bit range Description 23 to 20 Initiator house code 19 to 16 Initiator device code 15 Initiator function ('1' = on, '0' = off) 14 to 12 Reserved 11 to 0 Macro pointer (bits 0 to 11)

5.4.4. Macro data.

Macro data starts with a timer offset in minutes (0 for instant to 240 for 4 hours). Following the timer offset is the number of elements within the macro (1 to 255). This is followed by the macro elements themselves: Packet = delay:data_size:macro_element(data) The macro elements are configured as follows: Basic command: Bit range Description 23 to 20 Command house code 19 to 16 Command function 15 to 0 X10 format device bitmap Bright or dim commands: Bit range Description 31 to 28 Command house code 27 to 24 Command function 23 to 8 X10 format device bitmap 7 Brighten first ('1') or simply dim ('0') 6 to 5 Reserved 4 to 0 Dim value (ranging from 0 to 22) Extended data commands: Bit range Description 47 to 44 Command house code 43 to 40 Command function 39 to 24 X10 format device bitmap 23 to 0 Extended code data Note: The timer offsets are relative to the previous timer value.

5.4.5. EEPROM Data Transfer.

The EEPROM is downloaded to the interface in blocks of 19 bytes. The first byte is the macro download initiator command byte (0xfb), followed by two bytes containing the actual EEPROM address (this does not need to be sequential, although it must not cross the 16 bit page boundary). 16 bytes of EEPROM data follows the EEPROM address. Once the interface has received the EEPROM data, it will return a checksum. If the checksum is correct, the PC will acknowledge (0x00) and after the data has been programmed into the EEPROM, the interface will return a 'ready' command (0x55) to indicate that it is available to process PC requests.

5.4.6. Example.

PC Interface Description 0xfb EEPROM download start byte (first block of data) 0x00 EEPROM address 0x0000 (lo byte) 0x00 (hi byte) 0x00 EEPROM offset to macro initiators 0x000c 0x0c (hi byte) 0x3e Day mask x 0111110 (.FTWTM.) 0x00 Start day [0..7] 0x6d Stop day [0..7] 0x49 (Event start time, Event stop time) x 120 minutes 0x00 Start day range [8], Event start time [0..6] 0x80 Stop day range [8], Event stop time [0..6] 0x00 Start macro pointer [8..11], Stop macro pointer [8..11] 0x1d Start macro pointer [0..7] 0x22 Stop macro pointer [0..7] Summary: Start day: 0x000 (Jan 1) Stop day: 0x16d (=365, Dec 31) Start time: 4 x 120mins = 08:00 Stop time: 9 x 120mins = 18:00 Start macro pointer: 0x01d Stop macro pointer: 0x022 0xff Timer table delimiter 0x6a Macro initiator house and device code (A4) 0x80 Macro function (On) 0x11 Macro pointer (0x011) 0xff 0xb8 Checksum from the interface 0x00 Checksum correct 0x55 Programming complete. Interface ready. 0xfb Second block of data 0x00 EEPROM start address (lo byte) 0x10 EEPROM start address (hi byte) 0xff Macro table delimiter 0x00 Macro: instant 0x01 1 element 0x64 House code A, function Dim 0x00 0x40 Bitmap: device #1 0x0b Dim level 11/22 = 50% 0x0f Macro: delayed by 15 minutes 0x01 1 element 0x64 House code A, function Dim 0x00 0x40 Bitmap: device #1 0x80 Brighten to 100% 0x00 Macro: instant 0x01 1 element 0x62 House code A, function On 0x56 Checksum from the interface 0x00 Checksum correct 0x55 Programming complete 0xfb Third block of data 0x00 0x20 EEPROM start address 0x00 0x04 Bitmap: device #3 0x00 Macro: instant 0x01 1 element 0x63 House code A, function Off 0x00 0x04 Bitmap: device #3 0x00 Zero pad for remainder of the data stream 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x8c Checksum from the interface 0x00 Checksum correct 0x55 Programming complete

6. Serial Ring Disable

It may be required, for the sake of 'trouble-shooting' to disable the serial ring (RI) signal, although undesirable as macros held within the computer will not operate, nor will the computer be able to track the system status. The following protocol will allow the serial ring (RI) signal to be enabled and disabled: Enable Ring: PC Interface Description 0xeb Enable the ring signal 0xeb Checksum 0x00 Checksum correct 0x55 Interface ready Disable Ring: PC Interface Description 0xdb Disable the ring signal 0xdb Checksum 0x00 Checksum correct 0x55 Interface ready The default state of the serial ring (RI) signal after a power on reset is enabled.

7. EEPROM Address (executed via macro initiator).

This command is purely intended for the CM11 and CP10. When the interface receives a fast macro initiator, or when a timer event is processed, it will immediately perform an asynchronous transmission of the EEPROM address that is subsequently processed. The command is of the form: 0x5b EEPROM address transmission 0xhh High byte of macro EEPROM address 0xll Low byte of macro EEPROM address This transmission is a one time transmission, and requires no hand-shaking as the interface may not be connected to the PC.

8. Set Interface Clock.

This command is purely intended for the CM11 and CP10. The PC can set the interface clock with an unsolicited transmission at any time. In addition, once the interface detects the absence of power, it will request the current time from the PC when the PC is available as follows: CM11: For a CM11, the time request from the interface is: 0xa5. The PC must then respond with the following transmission Note: The bit range is backwards from what you'd expect in serial communications. Bit 55-48 is actually the first byte transmitted, etc. To make matters worse, the bit orientation is correct within the bit range, IE bits 4-7 of byte 6 _IS_ the monitored house code. Further, bits 0 and 1 of byte 6 appear to be flipped. I get a "monitor status clear" if bit 0 is set. The original docs had bit 23 as part of current hours AND day. DBS Jan 1, 1997 Bit range Description 55 to 48 timer download header (0x9b) (byte 0) 47 to 40 Current time (seconds) (byte 1) 39 to 32 Current time (minutes ranging from 0 to 119) (byte 2) 31 to 24 Current time (hours/2, ranging from 0 to 11) (byte 3) 23 to 15 Current year day (MSB is bit 15) (byte 4+.1) 14 to 8 Day mask (SMTWTFS) (byte 5-.1) 7 to 4 Monitored house code (byte 6...) 3 Reserved 2 Battery timer clear flag 1 Monitored status clear flag * See note 0 Timer purge flag * See note CP10: For a CP10, the time request is from the interface is: 0xa6. The PC must then respond with the following transmission Note: same as for the CM11. Bit range Description 63 to 56 Timer download header (0x7sb) 55 to 48 Current time (seconds) 47 to 40 Current time (minutes ranging from 0 to 119) 39 to 32 Current time (hours/2, ranging from 0 to 11) 31 to 23 Current year day 22 to 16 Day mask (SMTWTFS) 15 to 12 Monitored house code 11 Reserved 10 Battery timer clear flag 9 Monitored status clear flag 8 Timer purge flag 7 to 4 Power strip house code 3 to 0 Power strip device code

9. Status Request.

This command is purely intended for the CM11 and CP10. The PC can request the current status from the interface at any time as follows: CM11: For a CM11, the status request is: 0x8b. The status request is immediately followed by: Note: This is really interesting. The btye order is reversed per the note in section 8. The last 3 bytes are each mapped to show a 1 in the bit position if the unit with value equating to the nibble (section 1) is set. Low byte comes first, hi byte second. Example: if unit 1 is on, the nibble = 6, so the mask would show 00...0100000 Note also that the hi bit of byte 6 must be multiplied by 256 and added to the decimal value of byte 5 (+1) to find the Julian date. DBS Jan 1, 1997 Bit range Description 111 to 96 Battery timer (set to 0xffff on reset) (Byte 0-1) 95 to 88 Current time (seconds) (Byte 2 ) 87 to 80 Current time (minutes ranging from 0 to 119) (Byte 3) 79 to 72 Current time (hours/2, ranging from 0 to 11) (Byte 4) 71 to 63 Current year day (MSB bit 63) (Byte 5+) 62 to 56 Day mask (SMTWTFS) (Byte 6-) 55 to 52 Monitored house code (Byte 7 lo) 51 to 48 Firmware revision level 0 to 15 (Byte 7 hi) 47 to 32 Currently addressed monitored devices (Byte 8-9) 31 to 16 On / Off status of the monitored devices (Byte 10-11) 15 to 0 Dim status of the monitored devices (Byte 12-13) CP10: For a CP10, the status request is: 0x6b. The status request is immediately followed by: Bit range Description 119 to 104 Battery timer (set to 0xffff on reset) 103 to 96 Current time (seconds) 95 to 88 Current time (minutes ranging from 0 to 119) 87 to 80 Current time (hours/2, ranging from 0 to 11) 79 to 71 Current year day 70 to 64 Day mask (SMTWTFS) 63 to 60 Monitored house code 59 to 56 Firmware revision level 0 to 15 55 to 48 Power strip house and device code 47 to 32 Currently addressed monitored devices 31 to 16 On / Off status of the monitored devices 15 to 0 Dim status of the monitored devices

10. Power-up Timer.

This command is purely intended for the CP10. The interface contains a power-up timer that will turn on the remote controlled sockets once it elapses on the assumption that the computer has failed to boot-up. If it receives a message ('Relay Open' or 'Relay Close', see item 7) from the computer before the timer elapses, then the time-out is canceled and the sockets configured in accordance with the message. The power-up timer is the fifth byte of the six byte transmission for the scheduled ring, and it is split into two nibbles. The upper nibble is a reload value and the lower nibble is the actual timer. Each timer tick is 2 seconds, so the maximum timer value is 30 seconds.

10.1. Transmission Protocol

The PC can define the delay after which the power strip will turn the controllable outlets on and off after detecting the PC turning on and off. Bit range Description 55 to 48 Power-up timer download header (0xcb) 47 to 40 Reserved (0x00) 39 to 32 Reserved (0x00) 31 to 24 Reserved (0x00) 23 to 16 Reserved (0x00) 15 to 12 Power-up time-out (multiples of 2 seconds, range = 0 to 30s) 11 to 8 Reserved (0x0) 7 to 4 Power-down time-out (multiples of 2 seconds, range = 0 to 30s) 3 to 0 Reserved (0x0) The interface will respond with a checksum excluding the header. If correct the PC should respond with 0x00, or download the correct value again. The interface will terminate the transfer with 0x55 indicating that it is ready to communicate with the PC.

11. Relay Control.

This command is purely intended for the CP10. The power-strip contains a relay that controls four extension sockets. These sockets are controllable via the PC with the following commands: Close Relay (sockets on): PC Interface Description 0xab Close the relay 0xab Checksum 0x00 Checksum correct 0x55 Interface ready Open Relay (sockets off): PC Interface Description 0xbb Open the relay 0xbb Checksum 0x00 Checksum correct 0x55 Interface ready

12. Input Filter Fail.

This command is purely intended for the CP10. The power-strip contains an input filter and electrical surge protection that is monitored by the microcontroller. If this protection should become compromised (i.e. resulting from a lightening strike) the interface will attempt to wake the computer with a 'filter-fail poll'. This poll signal takes the form: Poll: 7 6 5 4 3 2 1 0 Value: 1 1 1 1 0 0 1 1 (0xf3) The poll signal will be repeated to the PC every second until the PC responds with the default poll response: PC Response: 7 6 5 4 3 2 1 0 Value: 1 1 1 1 0 0 1 1 (0xf3)