Murata Electronics North America XDM2140 Benutzerhandbuch

Packet Timing

Figure 8

9.0 Command Set

9.1 Command Data Types

Table 17 below defines the data types used in the commands:

Command Data Types

Length

unsigned long

4 bytes

unsigned short

2 bytes

unsigned char

1 bytes

Table 17

9.2 Command Format

X D M 2 1 4 0 C o m m a n d F o r m a t

0 x 7 E

H D L C C o n t e n t

1 6 - b i t F C S

C o m m a n d T y p e

M e s s a g e P a y l o a d

F r a m e S t a r t D e l i m i t e r

( B y t e 0 )

F r a m e D a t a

( B y t e 1 t o B y t e n )

F r a m e C h e c k S e q u e n c e

( B y t e s n + 1 , n + 2 )

F r a m e E n d D e l i m i t e r

( B y t e n + 3 )

C o m m a n d

( B y t e 1 )

P a y l o a d

( B y t e 2 t o B y t e n )

Figure 9

HDLC Packet Structure

The command type indicates which API message is contained in the message payload. The message
payload for each command type is described within the following sections. The length of the message
payload is 80 bytes (excluding byte-stuffing bytes).

The frame checksum (FCS) is calculated based on the 16-bit FCS computation method (FCS-16, RFC
1662). The XDM2140 checks the FCS and drops packets that have FCS errors. All numerical fields in a
packet are in big-endian order (MSB first), unless otherwise noted. Section 9.4 provides an example of
HDLC packet construction and HDLC packet decoding.

Table 18 provides a summary of XDM2140 commands, which are described in detail in the following
sections. For error handling, all other packet types should be ignored. The Destination column indicates
whether the packet is sent (or received) through the network or processed locally by the XDM2140.