Rice Lake SCT20-AN, Technical Manual

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SCT Weight Transmitter – 20 Series Technical Manual
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3.13 Fast Continuous Transmission Protocol
This protocol allows for continuous serial output at high update frequencies. Up to 300 strings per second are transmitted (with
a minimum transmission rate of 38400 baud).
The communication modes available are (
Section 2.4 on page 16 ):
•  : communication compatible with TX RS-485 instruments.?
•

: communication compatible with TD RS-485 instruments.?
If  is set, the following string is transmitted to PC/PLC: xxxxxxCRLF.:
In the event of negative weight, the first character on the left acquires the value « - » (minus sign - ASCII 45).
In the event of error or alarm, the 6 weight characters are replaced by the messages found in
Table 3-2 on page 30 .
If

is set, the following string is transmitted to PC/PLC: &TzzzzzzPzzzzzz\ckckCR
In the event of negative weight, the first character on the left acquires the value « - » (minus sign - ASCII 45).
In the event of error or alarm, the 6 gross weight characters are replaced by messages. See
Table 3.5 on page 30 .
Fast Transmission Via External Contact: A single string can be transmitted by closing a digital input, not exceeding 1 sec.
See Section 2.4 on page 16 and Section 2.10 on page 24 .
3.14 Continuous Transmission Protocol
Using this protocol, the instrument transmits, in continuous mode, the weight to remote displays; the communication string is
transmitted 10 times per second. The communication modes available are ( Section 2.4 on page 16 ):
•

: remote display shows the net or gross weight, depending on the remote display setting.
•  : remote display shows the net or gross weight, depending on the remote display setting.
•

:
The instrument sends the following string to the remote display:
• &NxxxxxxLyyyyyy\ckckCR
String Character Definition
xxxxxx 6 ASCII characters for gross weight (48 ÷ 57 ASCII)
CR 1 character of carriage return (13 ASCII)
LF 1 character of line feed (10 ASCII)
Table 3-46.  Communication String Definitions
Data Definition
& 1 character of string start (38 ASCII).
T reference character for gross weight.
P reference character for gross weight.
zzzzzz 6 ASCII characters for gross weight (48 ? 57 ASCII).
\ 1 character of separation (92 ASCII).
ckck
2 ASCII control characters calculated considering that the characters between
&
and
\
are excluded. The control
value is obtained by carrying out the XOR (or exclusive) operation for the 8 bit ASCII codes of the characters
considered. A character expressed in hexadecimal is thus obtained, with 2 digits which may acquire values from
0
to
9
and from
A
to
F
.
ckck
is the ASCII code of the two hexadecimal digits.
CR 1 character for string end (13 ASCII).
Table 3-47.  Communication String Definitions
Data Definition
& 1 character of string start (38 ASCII)
Table 3-48. Continuous Transmission Protocol Data Definitions