104S
♦
ProLinx Gateway
Reference
(Firmware v3.00 and later)
Protocol Manual
ProSoft Technology, Inc.
Page 125 of 157
January 22, 2010
5.2 SNTP
Support
SNTP is used for time synchronization of produced and consumed commands.
When an exchange occurs the driver compares time stamps from the previous
exchange. When the new exchange time is less than the previous exchange, the
exchange is ignored. This can occur when the Ethernet packets are routed and
delayed. Time synchronization provides for data integrity. The following table lists
the parameters defined in this section:
The SNTP driver will compute a new clock value every 5 minutes using the average
value of 10 samples each collected over an approximate 6-second period. This new
value will be used to adjust the clock maintained by the SNTP driver and used by the
application. If a valid database register is specified, the driver will place the time
value into the gateway’s database. The first two registers will contain the number of
seconds and the next two registers will contain the number of microseconds since
January 1, 1970.
A list of some of the common NTP servers can be obtained at http://www.ntp.org/,
http://www.eecis.udel.edu/~mills/ntp/servers.html, along with the appropriate IP
address. Other server lists can be found on the Internet by searching on "NTP
Servers" with your browser.
5.2.1 SNTP Status Data
The status data for the SNTP driver is located at the virtual database addresses
shown in the following table. The data area is initialized with zeros whenever the
gateway is initialized. This occurs during a cold-start (power-on), reset (reset push-
button pressed) or warm-boot operation (commanded or loading of new
configuration).
SNTP Client Status
4030 Time
is
valid
4031 Request
count
4032 Response
count
4033 Computation
count
4034 Clock
set
count
4035
Timeout error count
The gateway’s data mapping feature can be utilized to move this data into the
gateway’s database area. This way the data can be made available to all drivers on
the gateway for use on any of the connected networks. If it is not mapped into the
gateway’s database, the data will only be available through the Configuration/Debug
Port.
The
Time is Valid
status register will be set to 1 if the SNTP time is valid. If the time
is not valid, the register will be set to 0. All the other registers are counters used to
determine the functionality of the driver.
This version of the driver supports SNTP Revision 3 and stratum between 1 and 14.
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