CCD_Rasnik straightness monitoring system

Controlling the Ras_Mux module

The Ras_Mux module is used in the CCD_Rasnik alignment monitoring system.

The basic module (one card) contains an 8 channel video multiplexer and 16 LED drivers. It is controlled via a Centronics port of a PC or any device that can generate a 7 bit dataword plus a strobe. The signals are TTL level.

The system can be extended to 64 channels. Suppose a system is build by connecting 4 slave modules to a master module. We then have 32 inputs and one output. The video outputs of the slaves are connected to the inputs of the master. The video output of the master goes to the framegrabber.

The parallel interface connects to the master module. There the bus is buffered. A flatcable goes from the buffer to all the slave inputs. The address switch on the slaves are set from 0 to 3. The address switch on the master is set to 8. This forces a mode change in the address decoding. The video multiplexer selection of the master is now derived from higher bits then the selection of the slave modules.

The LED drivers have no function on the master.

When two cards are used to connect E.G. 16 video lines to 2 inputs of a framegrabber, there are only slaves. One of the slaves buffers the parallel interface for the other card.
The addressing of the video multiplexer and LED drivers is done in two stages. First an address is send, then one or more controlwords.

parallel interface
dataaddresscontrol
701
60X
5A5X
4A4VIDEO
3A3DUAL
2A2D_L
1A1A_B
0A0LED

meaning of the controlbits
VIDEO0the setting of the multiplexer is not changed.
1the address send is used to set the multiplexer.
DUAL0one out of eight drivers can be enabled.
1one out of four drivers can be enabled.
D_L0switch the addressed LED off.
1switch the addressed LED on.
A_B0select the A LED.
1select the B LED.
LED0nothing is changed in the LED outputs.
1the selected LED register copies the D_L bit.

After the address is sent, the controlword determines whether the video multiplexer has to be changed, an other LED is switched on, or both. Switching on an LED in the same group of 8 (or 4 when DUAL is active) automatically switches off the previously selected LED. Writing a zero into the LED register enabled last, switches all LEDs off. Writing a zero in an already inactive LED register has no effect. Neither does it affect other channels.

When power is switched on, video channel 0 is selected. All LEDs are switched off.

Go to the Ras_Mux home page or to the CCD_Rasnik home page.
You can mail suggestions for (or questions about) this page to: Henk Groenstege.
july 1996