GMB Instructions

What the GMB does

• RPC dark currents
• temperatures
• low voltage for FEC power.

• The GMBs are located physically in special crates, that they share with the multiplexes of the single rate counting system.
• The GMBs are connected to the IFR detector control system through a CANBUS. The CAN bus is driven by a CAN controller located in the VME crate of the IFR IOC.
• The IFR detector control system has 4 CAN buses:
  1. CAN0: barrel
  2. CAN1: barrel
  3. CAN4: forward endcap
  4. CAN6: backward endcap
• The GMB is identified on the bus by a HARDWARE ADDRESS that is WRITTEN ON THE BOARD. This is very important! The position of the GMB in a crate doesn't play any role. That means that when you replace a defective GMB, you need to make sure that the new one has the same hardware address written on it.
• To write a hardware address on a GMB, you need a PC with a PC CAN controller and a special software. Ask one of the following people (in this order):
  1. Ray Rodriguez
  2. Mark Freytag
  3. Dave Nelson
  Thy all have the necessary hardware and software.
• The GMBs are connected to the CAN bus in a daisy chain. The CAN bus needs to be terminated at the last one.
• The GMB has 4 LEDs on it, that each indicate something (picture coming):
  1. 2 green LEDs telling you the GMB is powered
  2. a third green LED telling you it sees the CAN bus.
  3. a yellow LED that goes on every time the GMB is read out.
  4. a red flashing LED that tells you it sees the bus clock. It is very hard to see.

Debugging GMB problems

• Values are not being updated, and the freshness number isn't changing.
• It is white in EPICS (lost contact with it).
• It is being updated but all (or a group of) channels of a GMB read the same value.

• Does the bus see the GMB? Use xyplex and scan the bus:

  [bbr-dev23] ~ > xyplex -f ifr-mon
  Trying 134.79.158.11...
  Connected to bbr-tty1.SLAC.Stanford.EDU.
  Escape character is '^]'.
  
  ifr-mon~> canScan "CAN0"
   BaBar Modules found:
      Station, Board Serial Number, Software Version: 1 29, 302
      Station, Board Serial Number, Software Version: 2 37, 302
      Station, Board Serial Number, Software Version: 3 33, 302
      Station, Board Serial Number, Software Version: a 2c, 302
      Station, Board Serial Number, Software Version: b 35, 302
      Station, Board Serial Number, Software Version: c 3a, 302
      Station, Board Serial Number, Software Version: d 24, 302
      Station, Board Serial Number, Software Version: e 10, 302
      Station, Board Serial Number, Software Version: 10 b, 302
      Station, Board Serial Number, Software Version: 11 4f, 302
  
   Wiener crates found:
      Status of crate 7b: ff
      Status of crate 7c: ff
  value = 0 = 0x0
  ifr-mon~> 
  

  If the GMB is not appearing there:
  1. power cycle the bus (LV-mon switches in electronics house)
  2. is there a GMB that should not be there in the upper list? If so, somebody may have replaced a GMB
  3. go to IR-2 and look at the board: bad contact?