Flow control

Flow control

Flow control is used in serial devices to allow them to better communicate when they are ready to send/receive data. For most devices it should be switched off, unless we know for sure that the device needs to use it. We have seen a number of cases in the past where having it on when not necessary has caused issues.

Flow control comes in two varieties, hardware and software.

Hardware flow control

Set off (probably the most used)

$(IFNOTDEVSIM) $(IFNOTRECSIM) asynSetOption("L0", 0, "clocal", "Y")
$(IFNOTDEVSIM) $(IFNOTRECSIM) asynSetOption("L0",0,"crtscts","N")

Set on using

$(IFNOTDEVSIM) $(IFNOTRECSIM) asynSetOption("L0", 0, "clocal", "N")
$(IFNOTDEVSIM) $(IFNOTRECSIM) asynSetOption("L0",0,"crtscts","Y")

in the device's st.cmd. To turn this off set it to N or remove the line completely. Under windows there is a further option to set it to D which ensures the hardware lines are floating (this is usually unnecessary).

Software flow control

In the device's st.cmd:

Set off using

$(IFNOTDEVSIM) $(IFNOTRECSIM) asynSetOption("L0",0,"ixon","N") 
$(IFNOTDEVSIM) $(IFNOTRECSIM) asynSetOption("L0",0,"ixoff","N") 

Set on using

$(IFNOTDEVSIM) $(IFNOTRECSIM) asynSetOption("L0",0,"ixon","Y") 
$(IFNOTDEVSIM) $(IFNOTRECSIM) asynSetOption("L0",0,"ixoff","Y")