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CVS4 Component Video Switch 

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CVS4 Component Video Switch

and the Error Response is always the string:

!ERR<CR><LF>

By parsing only the prefix characters ‘+’ and ‘!’, a programmer can chose to ignore the error 

codes and simply look at the first characters of the response strings and use them as a pass / 

fail indicator when issuing a command.
All response strings always end with a 

<CR><LF>

.

A Query Response string always starts with the ‘=’ characters and is followed by a command 

string indicating the parameter being returned. This is better explained in an example.
Here’s an example of a querying a device for its light intensity settings:

LI?<CR>       

Sent: Light Intensity Query command

+<CR><LF>     

Received: Acknowledgement of command

=LI 2,13<CR><LF> 

Received: Light Intensity Query Response

Note that a “

+<CR><LF>

” followed the command string. A command string is 

always

 followed 

by either an Acknowledgment (as in this case) or an Error Response. This consistancy allows a 

driver to use a single routine to issue a command and check for an Acknowlegement or an Error 

Response String, whether or not the command queries for a response.
An example of an error response:

IL?<CR>   

Sent: Command characters transposed, no such command

!2<CR><LF> 

Received: Error Response indicating unknown command

In this case the Error Response string “

!2<CR><LF>

” was issued instead of the acknowledg-

ment string since the command was not recognized.

Response String Checksums and CRC-8 Checkcodes

Response strings can be programmed to have checksums or CRC-8 checkcodes appended to 

them, the syntax is identical to the Command Structure’s checksum and CRC-8 handling.
Checksum and CRC-8 are turned on and off by issuing the proper command. On most devices 

this is the 

“Control Settings”

 command.

Only the Error Response and The Query Response strings will have checksum and CRC-

8 checkcodes appended to them. The Acknowledgment Response will always consist of 

“+<CR><LF>”. Anything else must be assumed to be a communication error.
An example with checksumming enabled, while querying for LED intensities is:

LI?<CR>

+<CR><LF>

=LI 2,13;239<CR><LF>

An example with CRC-8 responses enabled is:

LI?:194<CR>

+<CR><LF>

=LI 2,13:87<CR><LF>

Notice that in the first example a checksum was not appended to the “

LI?

” command. When 

issuing a command the checksum and CRC-8 codes are sent on a command by command 

basis. Anytime a checksum or a CRC-8 code is appended to a command it will be checked and 

validated by the device, regardless of the “Response Checksum / CRC-8” settings.
When Response Checksums, or Response CRC-8 Checkcodes are enabled, Error Response 

strings will also have checksum and CRC-8 codes appended to them.

Master / Slave and Asynchronous Modes of Operation

The K.I.S.S.™ protocol can be used in a Master / Slave mode, where responses are only sent 

when requested, or in an Asynchronous mode, where responses are sent whenever the opera-

tional state of the device changes, such as a front panel button being pressed.

The Master / Slave Mode of Operation

In the Master / Slave mode, the controller requests information from the device at polled 

intervals. The control program assumes the role of the master, and the device is operated in the 

slave mode. No information will be sent from the device without first receiving a request from the 

controller.
For controllers that cannot handle having information being sent to them in the background, or at 

unspecified times, the Master / Slave setting is ideal, since all state changes will be logged but 

not sent until requested by the controller.
To allow for more efficient Master / Slave operations, there is a Query Status command available 

to the controller that return the status state of the device as a bitmap of flags indicating which 

states have changed and need querying. This allows the controller to poll, using a single com-

mand, and then based on those flag settings, issue only the commands needed to read the new 

state(s) of the device.
The Master / Slave mode also allows for a predictable communications flow. A communication 

sequence is always started by the controller by issuing a command. The response will always be 

either the Acknowledgement Response, or an Error Response, followed by (if a query command 

was issued) the Query Response. For instance:

LI ?<CR>      

Sent: Controller issues a query command.

+<CR><LF>     

Received: Acknowledgment (or possible Error) Response.

=LI 2,13<CR><LF> 

Received: Query Response.

In the Master / Slave mode, the Acknowledgement or Error Response will always be the next re-

K.I.S.S.™ 

(Continued)

K.I.S.S.™ 

(Continued)

Summary of Contents for CVS4

Page 1: ...Z E K T O R Home Theater Switches Digital Video Component Video Multichannel Audio Rev 2 07 25 2006 High Definition Component Video Switch CVS4 Supplement to the CVS4 User Guide...

Page 2: ...ttings 19 Control Settings HDS4 2 Version 20 Extended Control Settings 21 Checksums and CRC 8 s 24 Checksums and CRC 8 Checkcodes Defined 24 Differences between a Checksum and a CRC 8 Checkcode 24 Sou...

Page 3: ...n this case the value defaults to the current setting leaving the value unchanged The K I S S Continued space before the comma is optional Most commands can be queried for their current settings by su...

Page 4: ...wed before the and characters but NOT after them The checksum must immediately follow the character and a CRC 8 checkcode must immediately follow the character anything else including whitespace will...

Page 5: ...R LF Notice that in the first example a checksum was not appended to the LI command When issuing a command the checksum and CRC 8 codes are sent on a command by command basis Anytime a checksum or a C...

Page 6: ...ghout the com munication sequence First the LI CR command was issued by the controller While looking for an Acknowledgement or Error Response string an unsolicited Query Response is received indicatin...

Page 7: ...Checkcode did not match the calculated one The command will be ingnored Error 5 The number of parameters given does not match the number allowed by this command Error 6 To prevent conflicts between th...

Page 8: ...HDS4 2 there is no space after the command in the response string Note 3 For backward compatibility with the HDS4 2 this response string is sent in the Asyn chronous mode when a channel status has ch...

Page 9: ...Where dim Current DIM level setting bright Current BRIGHT level settings The intensities range from 0 Off to 44 Maximum brightness Note For backward compatibility with the HDS4 2 there is no space af...

Page 10: ...earn they are IR Cmd Description 1 Power Toggle 2 Select Input 1 3 Select Input 2 4 Select Input 3 5 Select Input 4 6 Discrete Power On 7 Discrete Power Off 8 Sequence Through Inputs Setting an ircmd...

Page 11: ...ess of any possible setup state it might be in The 0 button code is also device independent It use and value does not change between Zek tor devices like the other codes may and most likely will Query...

Page 12: ...ro keeps the CVS4 from responding to IR codes however the front panel sensor remains operational and any codes received can still be queried for by using the IR command Disabling the IR jack by settin...

Page 13: ...al Value 128 64 32 16 8 4 2 1 Bit Position 7 6 5 4 3 2 1 0 Name CTL LMO IRC IRR BTN LIN SEL PWR Factory Settings 0 0 0 0 0 0 1 1 PWR 1 Power State has changed SEL 1 Selection Input Output Mapping has...

Page 14: ...Checksum and a CRC 8 Checkcode A CRC is capable of finding many more and different types of errors than a checksum can A good description of its capability is described in the above referenced articl...

Page 15: ...detection characteristics So x 8 x 6 x 3 x 2 1 101001101 14D hex Ignore X 8 01001101 4D hex Reverse bit order 10110010 B2 hex define CRC8_POLY 0xB2 polynomial mask define CRC8_INIT 0xFF initial value...

Page 16: ...28 CVS4 Component Video Switch 29 CVS4 Component Video Switch This page left intentionaly nearly blank This page left intentionaly nearly blank...

Page 17: ...Z E K T O R Z E K T O R 12675 Danielson Ct Suite 401 Poway CA 92064 858 748 8250 www zektor com...

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