dCS 904 User Manual

Manual for Software Version 1.5x and 1.36

dCS Ltd

June 2000

 

 

Command Streams

Example – a system of 9 units with ID’s set up as noted: 1 Master Clock (ID 1),

4P3D compatible ADCs (ID 2, 3, 4 and 5),

4P3D compatible DACs (ID 6, 7, 8 and 9).

RS232 operating at 1200 baud.

It is assumed that the transmitter operates on a round robin polling scheme and that each step completes before the next allowing for time outs. Except in the case of a time out a unit should not be accessed within the response time of its previous command. Within each step there is no need to wait for the command response time prior to moving on to the next unit – once an acknowledge has been received, the controller can safely assume that the unit is getting on with the command it has received, and can move on to the next unit. At the end of a step there is no need to wait before moving on to the next step.

Command strings are not given fully, the parameter string and the checksum are not explicitly given. A typical command is shown as:

[ID][Command Type], information about command

A typical response is:

[ACK Type][ID], information (when requested)

When changing the operating frequency of a unit the internal crystals are switched. It is recommended that after a crystal switch units are allowed to settle for a short time (< 1 second) to ensure optimum performance. In this case the units are being controlled by a Master Clock, so time should be allowed for this to switch and for the other units connected to it to also switch and begin to settle. It is recommended that there is no RS-232 activity for 3 seconds after the Master Clock frequency is switched to ensure all units have time to settle.

When operating in DSD mode units assume their reference clocks are operating at 44.1kHz. If a different frequency reference is used they will continuously monitor the reference clock frequency, preventing RS-232 accesses. It is therefore important to ensure the reference clock is set to 44.1kHz prior to entering DSD mode, and that DSD mode is left prior to changing the reference clock to another frequency.

Example: Switching to 96k PCM

The following example covers the system of nine units, in two complex format changes. Change the ADC and DAC operating mode to PCM prior to changing the Master Clock frequency. Change the DAC operating mode prior to the ADC. When changing the Master Clock frequency the system should be allowed to settle to the new frequency before any further RS-232 activity.

1)Command DACs 6, 7, 8 and 9 to change mode, the units may take up to 15 seconds to complete this command (if the previous mode had been DSD the FPGAs need to be re-loaded, which takes time). There is no need to wait prior to moving on to step 2.

Transmit -> [6][DSD_MODE], to change mode to PCM of unit 6 Responds -> [ACK 15 seconds][6], requested mode

Manual part no: DOC135904 iss 2B2

Page 56

135904ma2b2.pdf file available from website

Contact dCS on + 44 1799 531 999

email to: more@dcsltd.co.uk

(inside the UK replace + 44 with 0)

web site: www.dcsltd.co.uk