Omega A2400 manual Chapter Delay Time Programming

Chapter 6

Delay Time Programming

Each A2400 contains user-programmable delays to properly sequence the transmission of data from a remote radio modem to a host computer. The delays are required to sequence an external transmit enable signal required by most radio modems. The external transmit enable signal most often used is the RS-232 Request to Send (RTS) signal.

The RS-232 RTS signal normally becomes active just before data transmis- sion begins, remains active while all data is transmitted and then is immediately turned off. This sequence is essentially the same when using radio modems. However, a certain amount of time is required after a transmit enable signal (RTS) is activated for the radio transmitter to turn on. Transmission of data cannot begin until after the transmitter is settled and ready. Since this period of time may vary from vendor to vendor, user- programmable delays are provided in the A2400. These delays can be set long enough to ensure that the transmitter is on. The delay times are specified using commands from the A2400 command set and are stored in nonvolatile memory.

The A2400 uses three programmable delay times to properly sequence the data applied to the radio modem. These delay times are called T1, T2, and T3.

T1 is used to allow the host transmitter to turn off. T1 may be set to guarantee a specified amount of dead time between the radio modem receive data and the leading edge of the RTS signal which is used to key the transmitter.

T2 is used to allow the radio modem transmitter time to stabilize. T2 is the time between the leading edge of the RTS signal and the beginning of data transfer.

T3 is the delay time between the last data character to be transmitted and the trailing edge of RTS which turns off the transmitter.

The three delay times each have a programmable range of 0 to 2000 ms and are specified using the standard D series data format ‘+#####.##’. The delay time values may be set to 1ms resolution. Use commands T1, T2 and T3 to specify the delay values. These commands are write protected and must be preceded by a write enable (WE) command.