INSTRUMENT MANUAL
VACUUM GAUGE MODEL MM200
160Phone:(215) 947-2500 fax:(215) 947-7464 e-mail:[email protected] web site:www.televac.com
MM-200_im REV M
Page 102 of 160
TELEVAC
ALTERNATE ADDRESS SCHEME FOR RS485
The scheme consists of prefixing the address with a printable character not normally used by the MM200.
Hopefully, at least one of the characters available will not be used by other types of units on the same bus as the
MM200's. The default characters are the dollar sign "$" for the unit address and the ampersand "&" for broadcast
commands. These characters can be changed. The table below lists available characters.
CHAR CODE CHAR CODE CHAR CODE CHAR CODE
"
A
'
F
: K
]
Q
# B
(
G
; L
{
R
$
C
)
H < M
|
S
%
D
*
I
> O
}
T
&
E
/
J
\ P
~
U
Even if MM200's are the only units on a particular bus, the main idea is to make it simpler to program.
The commands that are used to install these characters are:
RI1<cr> is used to insert a new address prefix, where 1 is the letter chosen from the above table. It is necessary to
use a code letter since the input buffer of the MM200 will ignore and not store the characters themselves. When
used, this prefix is followed by the same unit address that is given in the RS485 protocol. The address is followed
by any of the normal valid RS232 commands. This is now done without parity or word length changes.
BI1<cr> is used to insert a different broadcast command prefix. The same table given above is used to select the
code letter associated with the desired character. When used, this prefix is followed by the broadcast command (no
unit address).
The alternate or standard mode of RS485 addressing can be selected with the following commands:
UA<cr> selects this new alternate method
US<cr> selects the previous standard method
Newly entered prefixes and the mode selection can be stored with the "SE<cr>" command. Use RS232 to enter
these commands.
SPECIAL COMMANDS
The following commands are available for test purposes but are not listed with the other normal commands. The
password is not required to use these commands.
"ES<cr>" Enable HV short detect
"SI<cr>" Inhibit HV short detection
"SD<cr>" Send hot cathode drive signal continuously.
"SS<cr>" Stop sending hot cathode filament drive.