Dynapro Technologies Dynapro ET TCS, Application Developer'S Manual

Page: 331 / 337

D-17
,QWHUDFWLRQ%HWZHHQ3RZHU8S,QWHUUXSW0RGHDQG0XOWLGURS3URWRFRO
The Power-Up Interrupt Modes provides a means for the host to be notified automatically
whenever the TCS regains power after an unexpected power loss. When Power-Up Interrupt
Mode is set, the TCS automatically generates an interrupt to the host indicating that power has
just been restored. This allows the host to take suitable actions to restore proper communication
with the user.
When the Multidrop Address is set to anything other than “none” indicating that the TCS and
host are to communicate using the Multidrop Protocol, then the Power-Up Interrupt M may not
operate as expected. When the TCS regains power when it was previously operating using the
Multidrop Protocol, there is no way for the TCS to tell whether it is still addressed by the host.
Even if the TCS knows it was previously addressed, it has no way of knowing how long it has
been without power and whether the host has unaddressed it in favor of another responding TCS.
Therefore, when the TCS regains power, it cannot safely connect its transmitter to the serial link
because it may corrupt communication between the host and another addressed TCS. Instead, the
TCS queues up the power-up interrupt in its output buffer and waits until it is readdressed before
transmitting the interrupt to the host.
For the host to use the Power-Up Interrupt Mode during multidrop operation, it must periodically
readdress the TCS to allow it to send its Power-Up Interrupt in case the TCS just regained power.
A preferred alternative would be to reset Power-Up Interrupt Mode and poll the TCS using the
Request Power Status command.