Introduction
Copyright IXXAT Automation GmbH
20
IEM Manual, 1.5
1.8.5 Software concept
1.8.5.1 Command channel
For basic interaction with immediate response between host and module, a
command channel is provided (see Figure 1-2 for an overview of the commu-
nication area in the DPRAM).
Commands are used for board initialization and channel access. The interface
functions of the command channel can be used either in blocking or non-
blocking mode. Blocking means that the function will return after the command
was executed and a result is available. Non-blocking means that the applica-
tion is responsible for receiving a result by polling with a corresponding query
function.
1.8.5.2 Service channels
Services provide a timeout controlled handshake messaging with request/
response and indication/confirmation mechanism between host and module.
A request is performed by the host and answered by the module by means of
a response. An indication is initiated from the module and answered by the
host by means of a confirmation. Size and layout of the transmitted data are
depending on the service. To avoid blocking, queues are used.
Services can be used depending on the protocol to access data. For example,
getting a value may be used from host to retrieve configuration data from the
module, in case of network access, the module may need host located data.
1.8.5.3 State control
The current state of the communication channel is represented by the MSM
(module state machine). The MSM is separated in a generic and a protocol
specific part. Access from command or service channel may be restricted by
the current state. State transitions between
PROTOCOL_OFFLINE
and
PRO-
TOCOL_ONLINE
are handled by protocol specific implementation. For better
readability, error states and sub states in case of a remote access are not
shown in Figure 1-5.
