35
ADVANCED USE MANUAL DD700
2.4.32 Keyboard lock
LK<CR>
Only the keyboard is locked and the
"
KEYLOCK" message is displayed
2.4.33 Keyboard unlock
UK<CR>
The keyboard is unlocked.
2.4.34 Command to change current unit of measurement (if secondary unit of
measurement is managed)
CU<CR>
(CUb<CR>)
2.4.35 Remote commands with checksum
During installation it is possible to enable remote command management with checksum.
Checksum mode increases communication safety between terminal and
PC as it adopts the following precautions:
each remote command sent to the terminal must contain two checksum characters, in relative
position;
each response with data that the terminal sends to the PC following a remote command must
contain two checksum characters, in relative position;
The position of the two checksum characters is immediately preceding the character <CR>.
The checksum calculation consists in running XOR (exclusive OR) of all the characters in the string
up to the first excluded checksum character. The result is expressed with two hexadecimal
characters.
The gross weight transmission command with checksum is provided below as an example:
XB chk1chk2 <CR>
where, if we assume that value A1 is taken from XOR:
chk1
is the first checksum character ("1" i.e.
31H)
chk2
is the second checksum character ("A" i.e. 41H).
The terminal responds with the following string:
n<SP><um><SP>B chk1chk2 <CR><LF>
n = 9 characters.
2.4.36 Remote commands with addressing
By selecting the "A richiesta con indirizzo" (On request with address) string or by selecting the
RS485 communication interface, it is necessary to add the number of the instrument being
interrogated to the remote commands described in
par.2.4
.
The system is comprised of a Master terminal (a PC, for example) and several Slave terminals
(weighing terminals, for example).
Each weighing instrument is distinguished by a unique, settable "terminal number".
Accordingly it is possible to create a network of weighing terminals interrogated by the Master
unit.
The syntax of the remote commands is modified by adding two terminal number characters.
For example, gross weight transmission command XB <CR> becomes XB 01 <CR> indicating that
the Master terminal requests the transmission of gross weight to the terminal identified by number
01. In the same way, in checksum mode, the gross weight transmission command becomes XB01
chk1 chk2 <CR>.
If there is a checksum error the terminal will not send any response
