User manual

Toolbox 32 User Manual 1.47d www.cse-semaphore.com/mykingfisher
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153
Driver - ASCII
The ASCII protocol allows a Kingfisher RTU to request information from an external device using an ASCII or
hexadecimal protocol. Data returned from the device is stored in network registers corresponding to the
address assigned to the ASCII device (note: an LP-1/2/3 stores the data in local registers).
The ASCII driver transmits a zero terminated string and then stores the received string in registers or scans
the string for floating point variables.
Each character is stored as an 8-bit ASCII number. Two characters are stored in each local register. For
each pair of characters, the left character is stored in channels 1-8 and the right character is stored in
channels 9-16. For an LP-1/2/3, the characters are stored in reverse order.
The string sent to the external device can be a fixed string entered in the ladder logic or a string stored in
local registers. The string must be zero terminated and can therefore not contain any zeros. The difference
between the RX_ASCII and TX_ASCII ladder functions is that the TX_ASCII ladder function sends a byte
string and returns a byte string. The RX_ASCII ladder function sends a byte string and returns a number of
floating point variables. The received message string is scanned for any digits. Each set of digits is
converted to a floating point value and stored in the network registers corresponding to the device address.
The number of floating point values returned is configured in the ladder block. If less decimal numbers are
found in the message than floating point values configured, the remaining floating point values are returned
as zero.
Tx ASCII
Comment: A 12-character description.
RTU Number: (1-249) The RTU address assigned to the ASCII device.
String: Characters to be sent or first local register (#R) where string is stored.
Max. bytes in reply: (1-200) Maximum number of bytes to return.
Reply # bytes: (#R1-#R2048) Specified using a local register but indicates the network register where the
number of bytes received is reported. Note: an LP-1/2/3 stores the data in local registers instead of network
registers.
Reply destination: (#R1-#R2048) Specified using a local register but indicates the first network register
where the received message bytes are reported. Note: an LP-1/2/3 stores the data in local registers instead
of network registers.