DekTec DTM-3237 DVB-S2 Receiver - Manual (Page 17)

DTM-3237 – OEM DVB-S2 Receiver with DVB-ASI Output
User Manual
17
When an incorrect checksum is detected, the DTM-3237 will not return an answer. When protocol-
errors are detected, e.g. a combination of a valid category with an invalid setting, the R/W byte of the
reply is replaced by the ASCII character ‘E’ and the data is removed from the message.
When a master starts writing to a device while the previous command is still being executed, the device
will ignore the data.
When a master starts reading from a device while there is no answer available (yet), the device will
reply with the value 0x00. The value 0x00 will be returned until an answer is available and the master
has initiated a new read transaction.
S and P are the standard I
2 C start and stop conditions.
Please refer to Appendix D for a communication example.
4.3 Manageable items
The tables in the sections below provide lists of variables that can be configured and/or monitored
using the USB, I 2 C or LVTTL serial control port interface. The ‘Access’ column indicates whether the
variable can be changed or not, according to the table below.
Access Description
RO Read only
WO Write only
R/W Read and/or write
R/Wusb Read from all interfaces, write from USB only
NA Not applicable
DE-XXX Delayed execution (see §4.4 - Delayed execution)
4.4 Delayed execution
Most items are processed directly when the read or write command is received, which will immediately
result in an action on the device. In contract to these directly processed items, some items require
more processing time and therefor these actions are performed with a delay in a background thread.
Items which execution is delayed are marked with a “DE” (delayed execution) prefix in the access
column.
Items which execution is delayed can be monitored by the “Busy” item (category 0x01, setting 0x0C).
During the execution of these items, the “Busy” item is set and it is not possible to execute other “DE”
marked items. In case the “Busy” item is set and a “DE” marked command is received, the device will
return with a ‘B’ (busy) result in the Read/Write field of the DTM protocol frame structure.