June Tech Tip - Transistor to Transistor Logic
The Neuralynx Cheetah Data Acquisition Software (DAS) is capable of reading transistor to transistor logic (TTL) input values and outputting TTL values via both dedicated add-on Digital I/O boards and through Neuralynx acquisition systems. These TTL's can either be "on" (voltage applied) or "off" (grounded). Neuralynx recommends using 5V for the applied voltage for TTL's.
Each TTL device has a specific number of physical TTL pins, otherwise known as bits, associated with it. To allow for more flexibility in configuring how Cheetah utilizes your available TTL bits, each TTL device has their total number of bits divided into ports (groups of TTL bits). You can then configure and use the bits on each port independently of the bits on other ports.
The Digital Lynx SX systems have four 8-bit I/O ports. This has been integrated directly onto the front of the SX systems. The Digital Lynx S systems offered a 16-bit TTL Parallel Input Port (also found on the front of the acquisition system). The Cheetah 32 (analog) system provides two 16-bit options via the use of the Cheetah Digital Interface.
The TTLs are accessible from two 34-pin connectors on the SX Motherboard front panel. Each 34-pin port includes two 8-bit TTL ports.
To utilize these ports, Neuralynx recommends the use of a 2-Pin BNC cable. This cable then provides a connection to a BNC device and also to the TTL Bit and Ground connection on the devices listed above. You must make sure that a ground is connected during the use of TTL's in order to make sure your voltage levels do not fluctuate. All pin outs are available within the specific User Manual for your convenience.
Our Cheetah software allows for these TTL values to be timestamped along with all other data that is being recorded. This is useful for both offline and online analysis. In order to set this up, you will need to open the Event Display Window (incoming TTL's). This can be found under the "View" menu within Cheetah, then by selecting "Event Display". For additional information regarding this window, please review the "Events" section located within the Cheetah Reference Guide ("Help menu", then "Cheetah Reference Guide").
For Cheetah 5.5 users, a Digital I/O Setup window is also included. This is where you can select the Input Ports and also the Output Ports. All of the available devices will automatically be listed within these windows, and also include all of the relevant information for the commands that are available. For a complete list of the available commands, please review the Digital I/O Commands found within the Cheetah Reference Guide.
Generating or receiving TTL pulses can be very useful for your recordings. By use of TTL's external stimulators can be added into your system setup, you could trigger an actuator, signify a threshold marker and a multitude of additional setup options. All of these TTL's would then be marked within Cheetah automatically. If you have any specific questions regarding TTL's, please contact firstname.lastname@example.org and we would be happy to assist you.