wilamowski-b-m-irwin-j-d-industrial-communication-systems-2011

45-10 Industrial Communication Systems
45.5.9 Diagnostic Frame
Diagnostic frames always carry transport layer data. There are two types, the master request frame
(MRF) and the slave response frame (SRF). The transmitter is always the master. The MRF has the ID
0x3C (60) and always has eight data bytes. It is the “go-to-sleep” command if the first byte carries 0x00,
otherwise it carries a transport layer protocol. The SRF transfers the slave response of the transport layer
protocol to the master. It has the ID 0x3D (61) and also has eight data bytes.
45.6 Network and Status Management
The network and the status management features are very simple. The network management feature
supports only the “wake-up” and “go-to-sleep” signals. The corresponding slave state diagram is shown
in Figure 45.9. The slave node enters the Initializing state after power-on, reset or wake-up. In the operational
mode state that the slave node can transmit and receive frames. In the bus sleep mode state, the
node is normally in power save mode. The bus line is set to the recessive level (logical 1). Any node can
send a wake-up request for the cluster. Each slave node can detect the wake-up request and listen for bus
commands for a short period. The master node can also wake-up and send frame headers to establish
the cause of the wake-up.
The slave nodes enter the bus sleep node if they receive the go-to-sleep command from the master or
if the bus is inactive for a minimum of 4 s. Bus inactivity means no transitions between logical 0 and 1
bit values and so covers the IDLE state and a short circuit condition with V SUP or GND.
For status management each slave node monitors its communication. The slave provides two status
bits for status management within its own node: error_in_response and successful_transfer. If it detects
an error (bit error, framing error, or checksum error), it sets the response_error signal. This is carried
as a one bit scalar signal in an unconditional frame to the master. The position in the frame is defined
in the LDF. Based on this single bit, the master node can interpret the error states as listed in Table 45.4.
Reset or power on
Wake up
signal
Initializing
Bus sleep
mode
Go-to-sleep
command
Operational
mode
FIGURE 45.9
Slave node state diagram.
Table 45.4 Interpretation of the Response_error
Signal by the Master Node
Response_error
False
True
The slave node did not answer
Interpretation
The slave node is
operating correctly
The slave node has
intermittent problems
The slave node, bus,
or master node has
serious problems
© 2011 by Taylor and Francis Group, LLC