Question about a tutorial wiritten by Norum

["Silver" <marco_hair@163.com>]

hi, all:

  I want to write a driver for one of our serial devices, so I read "How to create EPICS device support for a simple serial or GPIB device". (http://www.aps.anl.gov/epics/modules/soft/asyn/R4-9/HowToDoSerial/tutorial.html)

While I have several questions:
  1. in the tutorial, it said:

Command array index 0 ? Device Reset
{&DSET_LO, GPIBWRITE, IB_Q_LOW, NULL, "\377\377\033", 10, 10, 
       NULL, 0, 0, NULL, NULL, "\033"}, 
I don't understand what's the meaning of "\377\377\033", does it mean "377" is oct number?

  2. in function "convertPositionReply" and "convertStatusReply", 
first time, pli->val = pdpvt->msg[0]; 
second time, pli->val = pdpvt->msg[1]; 
Does it mean the AB300's response data begin from different position? can anyone give me some explanation?
I have never used GPIB device before, so forgive my innocence.
Thanks a lot in advance.


Best regards
Geyang  2008-09-30