User Tools

Site Tools


serial

Table of Contents

Serial

Used to set parameters related to the device's serial ports.

There are tabs for basic and advanced parameters. Advanced parameters typically do not require adjustment.

Basic

Baud Rate Set the serial baud rate for the input and output ports. Each port can have different baud rates and formats if necessary.
Parity Set the parity used by the connected devices if any. Options are Even, Odd, or None.
Data Set the number of Data bits in the serial frame. Options are 7 or 8.
Stop Set the number of Stop bits ending the serial frame. Options are 1 or 2. 1)
Timeout Set the No-Response timeout for the SS20. This is the maximum time the SS20 will wait for a full response from the slave device before giving up and sending the next message in the queue. The timeout timer is started at the end of the transmitted request and ended by the receipt of a full response packet. 2)
(see appendix for more information)

Advanced

Byte Delay Shows the Modbus RTU standard inter-character delay in milliseconds for the selected baud rate. Timing based protocols such as Modbus RTU use a specific period of silence after the last received character to determine the end of a message packet. This is typically equal to 4 character times (1ms/char * 4 char times = 4ms at 9600 baud).
Delta Delay Set an additional time in milliseconds to add to the standard Byte Delay for inter-character timeout. This setting can be increase to repair packets fragmented by packet radio networks or slow devices.
RTS Keying Enable RTS keying if an RTS signal is required to key a radio or modem to transmit or if a delay before transmission is desired.
Key Delay When RTS Keying is enabled this sets the time in milliseconds that the device will wait after raising RTS before sending the data message.
BSAP (NEW!) Enable bristol BSAP protocol support - Allows BSAP messages to be properly transferred as well as supporting address blocking/passing and Com Watchdog functions for BSAP. Other protocols such as Modbus and ROC can still be utilized in conjunction when BSAP is enabled.3)
BSAP Delta When a BSAP message is detected this setting determines the maximum time to wait for additional characters until a DLE ETX command is received or timeout occurs.4)
CRC Cyclic Redundancy Check - Check box to force the SS20 to only pass messages containing a valid Modbus RTU CRC.
BR Byte Removal – When Checked, 0xFF characters will be discarded if at the beginning of a message. Use this setting if certain types of noise (Typically Data Carrier key noise) are causing spurious start bits to be received at the beginning of transmission.
1) Most Modbus RTU devices use a 8:N:1 data format.
2) It is critical that this setting be set longer than the maximum typical response time from the Slave device and that the No-Response timeout in the Master or Host device be set to double this value. The typical response time can easily be determined by monitoring the data transactions in TAP mode with the GUI’s Monitor window.
3) This setting may negatively affect passing Modbus/ROC messages for RTU address #16 in some situations
4) The BSAP Delta for the output port should be set to less than the no-response timeout on the Serial>Basic tab
serial.txt · Last modified: 2017/01/12 09:47 by jwilliams