62
Blanks must be put on the tail for all items in order to have
always a total length of 6 characters (see the setup table) .
The same parameter format used for setup item set-
ting is used also for setup item getting (i .e . when a
“
NN
GET
CNN
<CR>” command is received from the PC,
the reply “
NN
<STX>
P
1
P
2
C
1
C
2
C
3
C
4
<ETX>” is sent back) .
To perform a “
NN
SET
CNN
. . .” command the general pass-
word has to be sent in advance through the “
NN
PWD . . .”
command . See above for the password effectiveness time-
out .
Some special setup items can not be set through RS485
commands . In particular it is not possible to access any setup
item that performs a test on the instrument and it is not pos-
sible to configure the hardware identifier (setup item G .12) .
The “
NN
SET . . .” and “
NN
GET . . .” commands when used
for password items, baud rate, hardware identifier, F .00
and F .10 items, P .00 through P .09 items, are answered with
“
NN
<CAN>” .
As soon as the process controller realizes that a command
has been received, it sends one of the following answers:
1) “
NN
”, ACK (char 0x06) if the process controller recog-
nizes the set command and performs the requested task;
2) “
NN
”, STX (char 0x02),
DATA
, ETX (char 0x03) if the
received command is a request of data;
3) “
NN
”, NAK (char 0x15) if the process controller does
not recognize the command or if the command syntax
is wrong;
4) “
NN
”, CAN (char 0x18) if the process controller can not
answer to the request (e .g . the current process model
does not support the request, the given general password
is wrong, etc .)
The “NN” in the front of the answer is the Process ID
(“00” to “99”).
