ACC-72EX User Manual
DPRAM Data Processing
57
Identifier
The ulId field is used to identify a specific packet among others of the same kind. That way the
application or driver can match a specific reply or confirmation packet to a previous request
packet. The receiving task does not change this field and passes it back to the originator of the
packet. Its use is optional in most of cases, but it is mandatory for fragmented packets. Example:
downloading large amounts of data that do not fit into a single packet. For fragmented packets,
the identifier field is incremented by one for every new packet.
Status / Error Code
The ulSta field is used in response or confirmation packets. It informs the originator of the packet
about success or failure of the execution of the command. The field may be also used to hold
status information in a request packet. Status and error codes that may be returned in ulSta are
outlined in Status and Error Code section.
Command / Response
The ulCmd field holds the command code or the response code. The command/response is
specific to the receiving task. If a task is not able to execute certain commands, it will return the
packet with an error indication. A command is always even (the least significant bit is zero). In
the response packet, the command code is incremented by one indicating a confirmation to the
request packet.
Extension
The extension field ulExt is used for controlling packets that are sent in a sequenced or
fragmented manner. The extension field indicates the first, last, or a packet of a sequence. If
fragmentation of packets is not required, the extension field is set to zero.
Routing Information
The ulRout field is used internally by the netX firmware only. It has no meaning to a driver type
application and therefore is set to zero.
User Data Field
The tData field contains the payload of the packet. Depending on the command or reply, a packet
may or may not have a data field. The length of the data field is given in the ulLen field.
