Multichannel Systems MEA-System Manual - Manual (Page 19)

Appendix
19
3.6 Digital Input / Output, System Synchronization
TTL stands for Transistor-Transistor Logic. A TTL pulse is defined as a digital signal for
communication between two devices. A voltage between 0 V and 0.8 V is considered
as a logical state of 0 (LOW), and a voltage between 2 V and 5 V means 1 (HIGH).
Warning: A voltage that is higher than +5 Volts or lower than 0 Volts, that is, a negative
voltage, applied to the digital input would destroy the hardware. Make sure that you apply
only TTL pulses (0 to 5 V) to the digital inputs.
3.6.1 Triggering the Data Acquisition and MC_Rack
The digital input accepts TTL pulses. This feature can be used for triggering the USB device
and MC_Rack, for example, for synchronizing stimulation and data acquisition.
For example, you can connect the Sync Out of a STG (stimulus generator) to one of the digital
input bits. If you use only one instrument for triggering, connect it to bit 0. In MC_Rack, add a
Trigger Detector to your virtual rack, and select the Digital Data D1 input stream as the Trigger.
Select the appropriate logical state (generally HIGH) for triggering. Mask all unused bits.
The standard settings of the Trigger Detector are for using bit 0.
Please see the documentation on the Recorder and on the Trigger Detector instrument and
on triggered data in the MC_Rack help or manual for more details.
Important: It is recommended to apply TTL pulses with a duration of at least 200 μs. Shorter
pulses may be ignored by the USB device. Please mask unused (not connected) digital input
channels in the MC_Rack program to ignore undefined states of the open inputs that can
cause unwanted trigger events. Please see the MC_Rack manual for more details.
3.6.2 Triggering other Instruments by MEA2100-System or USB-Device
The digital output of the USB device generates and sends 20 ms TTL pulses (0 V = LOW and
5 V = HIGH). This feature can be used to apply a feedback triggered by a signal or a parameter
stream.
For example, you can connect the “Trigger In” of a stimulus generator (STG) to the digital output
via the “Digital IN / OUT” connector. You can also use the digital output for a synchronization of
the (USB-) MEA-System with other systems, for example, for Calcium imaging or video tracking,
provided that the other system of choice is able to receive TTL pulses.
Please see the documentation on the digital output instrument in the MC_Rack help or manual
for more details.