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When Alternate Packing is enabled, the Pack Control settings become available. As shown in table 7-9 on page 54 of the User Guide the possible settings for the gap timer are 12ms, 52ms, 250ms and 5 seconds. Most folks use either 12ms or 52ms, the higher values will only work if there is very sparse data coming into the serial port and if the data is not very time sensitive.
For instance, if you use 5 seconds as the gap timer and a single character is received about every 4 seconds the data may not be sent until the MTU (Maximum Transmission Unit) value is reached. With the default MTU of 1400 it could take a while to get a packet together to send in this scenario. No matter what the pack control settings are the UDS will always send a packet when its buffer reaches the MTU value.
You can also allow trailing characters (e.g. a CRC or Checksum) and configure the handling of Send Characters. See the description of these options at the top of page 55 of the User Guide referenced abote. Defining Send Characters is documented a little farther down on page 55, after the section on DisConnTime.
For instance, if you have a serial device that sends data "packets" that always end with the same one or two characters you can force the UDS to pack each data "packet" into an ethernet packet and send it when it detects those characters.
Also see:
FAQ# 11 - Cobox, UDS10, UDSx00, SDSx100, XPort, WiPort - Packing Algorithms
http://ltxfaq.custhelp.com/cgi-bin/ltxfaq.cfg/php/enduser/std_adp.php?p_faqid=11Cobox, UDS10, UDSx00, SDSx100, XPort, XPort Direct, WiBox, xDirect, xPico or WiPort - Packing Algorithms
FAQ# 1015 - Using Pack Control For UDS, SDS, XPort, WiPort & WiBox Products
http://ltxfaq.custhelp.com/cgi-bin/ltxfaq.cfg/php/enduser/std_adp.php?p_faqid=1015Using Pack Control For UDS, SDS, xDirect, xPico, XPort & WiPort Products
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[Originally Published On: 03/30/2009 04:51 PM]