Choice of interface

Sending commands or remote transfer of files to the VTAP reader will require at least one of the USB ComPort, RS-232 serial, RS-485 serial or TTL serial interfaces. These are called the VTAP 'Command Interface(s)'.

Three common implementations are:

1. One of the serial ports is used for sending commands and file transfer, while pass payload is sent over USB keyboard emulation;

2. The USB ComPort is used for sending commands and file transfer, with pass payload sent over a serial RS-232 interface;

3. Pass payload, sending commands and file transfer all use a single type of serial port, in passive mode. (If you are using command-response actions and receiving routine data on the same interface, choose passive mode to avoid the risk of pass reads interrupting other actions.)

   Active or passive interface

   The USB or serial communication interfaces, can be described as being in either active or passive mode.

   Active mode means that pass payload or card data read by the VTAP reader will be
   sent immediately over the interface in use, whenever it is read. Active mode allows simultaneous bi‑directional communication, such as continuous reception of any incoming data from the reader and sending any commands. (Active mode is not therefore suitable for RS-485 where communications are half-duplex.)

   Passive mode means that the VTAP reader will only send data in response to a command (query), listed in Data request commands. Passive mode is useful if your system or application polls for data to process, rather than reacting to data which could arrive at any time. It ensures that data received can always be treated as a response to the last command sent. Passive mode allows uni‑directional communication only, and so is recommended for the RS-485 interface as that is half‑duplex. It can also be used, on any of the full‑duplex interfaces on your VTAP reader (USB COM, serial RS-232, TTL serial), if required for your application.

Your preference is likely to be driven by your existing systems, and in‑house technical expertise.

If you need pinouts and hardware connection information please refer to the VTAP100 mechanical installation, VTAP50 mechanical installation or Wiegand wiring (for model VTAP100-PAC-W only) as appropriate for your VTAP reader.

Choice of interface table presents all of the interface options and their pros and cons.