Communications Manual Rev 3.10  Software Versions 3.xx 
Page 16 
003R-618-310
 
4.1.3.  Register Id Field 
This is the four character hexadecimal register identifier.  For the list of registers in 
the instrument refer to Register Identifiers page 38. 
4.1.4.  Optional Parameters 
The value here is dependent on the command and register being accessed.  Not all 
commands require a parameter (eg. CMD_READ_FINAL).  Commands that write to 
a register have the new value as the parameter. 
4.1.5.  Return Value 
The  value  here  is  dependent  on  the  command  and  register  being  accessed.    If  a 
command does not return a value (eg. CMD_WRITE_FINAL), then the return value 
will be an error code (eg. “0000” for no errors). 
4.1.6.  RS-232 Ring Network Enhancement 
When  the  instruments  are  installed  in  a  Ring  Network,  the  central  computer’s 
software is required to send additional framing characters around each command. 
Referring  to  Table  2  COMM  Command  Format  above,  the  enhanced  commands 
from a Master (typically a PC) to the instruments are of the format: 
Echo-On  COMM Message  Echo-Off 
<DC2> 
Command: 
Address 
Field 
Command 
Field 
Register Id    [Optional 
Parameter] 
 
xx  mm  rrrr  “:”  [ppppp] 
  
 
<DC4> 
Table 4 COMM Command Format with Ring Network Enhancement 
Where: 
<DC2>  and  <DC4>  are  the  characters  ASCII 12
 H
  and  ASCII 14
 H
  respectively, 
here called ‘Echo-On’ and ‘Echo-Off’. 
Each instrument echoes the command, which is passed on to the next instrument. 
If  the  command’s  Address  Field  is  addressed  to  one  of  the  instruments,  or  is  a 
broadcast (Address Field = 0), then the instrument will append a response ahead of 
the ‘Echo-Off’-<DC4> character. 
If  the  command  is  broadcast,  every  instrument  will  append  a  response:  eg.,  7 
instruments will generate 7 responses. 
Referring  to  Table  3  COMM  Response  Format  above,  the  responses  from  each 
instrument that are sent onto the next instrument, and so on up to the PC, are of the 
format: 
Echo-On  COMM Message(s)  Echo-Off 
<DC2> 
Command: 
Address 
Field 
Command 
Field 
Register Id    [Optional 
Parameter] 
 
xx  mm  rrrr  “:”  [ppppp] 
  
’n’ Responses: 
Address 
Field 
Command 
Field 
Register Id    Return 
value 
 
yy  mm  rrrr  “:”  vvvvv 
  
 
<DC4> 
Table 5 COMM Response Format with Ring Network Enhancement