Model VM32PAFF
32 Channel VME Module
Programmable Amplifier
Description
With Fixed Frequency Filter
5
1784 Chessie Lane., Ottawa, IL 61350
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Tel: 800/252-7074, 815/434-7800
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FAX:815/434-8176
e-mail: [email protected]
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Web Address: http://www.freqdev.com
3.
Description
The VM32PAFF is a single width B-size (6U) VME model that consists of a motherboard and up to 32
daughter modules. The motherboard contains the VMEbus interface and input and output connections.
Each daughter module is made up of two boards: a high precision programmable gain amplifier board and
a 3-pole filter/buffer amplifier combination board.
VME Bus Interface and Input/Output Connections
The VM32PAFF appears on the VMEbus as a Revision C.1 compliant A16/D16 slave. The VMEbus
backplane offers a software programmable interface to set the gain of each daughter module. Through the
interface, a user can also read back individual channel gain settings. This VM32PAFF read/write or bi-
directional access to the individual amplifier modules is especially useful when building auto-ranging
systems and/or fault tolerant systems. Additionally, it is good for diagnosing system failures, for debugging
newly developed systems, and for constructing reliable test header files.
The motherboard uses an indexed channel addressing scheme and transfers gain data to/from the
selected channel over a simple serial channel.
Figure 3-1
is a simplified block diagram of the VM32PAFF
showing one amplifier/filter channel and all of the common functions.
The serial channel incorporates some features that are especially important when providing precision, low
noise signal conditioning. When the board is not being accessed (the normal case during a test) the serial
channel is entirely static. When the board is accessed to set or read back a channel gain, only the channel
being accessed is clocked, so the other channels on the board see no logic transitions that could inject
noise or induce DC offsets.
The serial channel is slow compared to VMEbus transfer rates. Rather than hold the VMEbus while gain
data is serialized and transferred to the selected channel, the VM32PAFF board uses a BUSY flag interlock
while data transfer to/from the selected channel is taking place.
The motherboard provides simultaneous access to up to 32 Differential - DC-coupled wideband input
signals. It offers up to 32 Single-Ended – DC coupled output channels in four groups of eight. Available
options include AC-coupled input channels and/or Differential output channels
