TB8100 Service Kit User’s Manual Configuring the System Interface 85Configuring External Channel SelectionUsually, the channel that the base station normally operates on is selected usingthe Service Kit (see “Default channel” on page 82). If you want the channel tobe selected by equipment external to the base station, enable external channelselection and configure the base station’s system interface to reflect the way thatequipment works. Then the channel number to use is computed from the stateof the digital inputs assigned to channel selection.To configure external channel selection1. Select Configure > Base Station > System Interface.2. In the Type list, select the system interface type that the base station is fittedwith, so that the pinout table displays the available pins.3. Select the Channel selection check box. This enables external channelselection.4. In the Pins to use box, select an option. For each bit in the binary channelnumber, you need a pin.The table to the left updates to indicate the bit number of each pin that willbe used for channel selection. Digital input 1 defines bit 0, digital input 2defines bit 1, and so on. The Number of selectable channels box updatesto indicate the highest channel number that the hardware will be able toselect.5. If the system interface uses any dual-purpose pins as digital outputs, clickMap Inputs and edit the mapping of digital inputs to channel selection bits,so that channel selection doesn’t use those digital outputs. For details, see“Mapping Digital Inputs to Channel Selection Bits” on page 85.6. Specify whether the external equipment selects the channel number usingbinary or BCD format.Important: The base station interprets a line as ‘1’ when it is active(when the external equipment is pulling it to ground, the voltage islow, and current is flowing).7. If the external equipment pulls a line to ground to indicate a ‘0’, select theInvert box.8. Use the Service Kit to test your setup. See “Testing Hardware ChannelSelection” on page 177.Note: Setting the channel to 000 (by switching all DIP switchesoff—or on, if the selection is inverted) disables external channelselection. The base station will operate on the channel selected bythe Service Kit or by Task Manager action.Mapping Digital Inputs to Channel Selection BitsNormally, channel selection uses the available digital inputs in order, eventhough some digital inputs are dual-purpose and can be used as digital outputs.You can however individually map each digital input to a particular bit that isused to select the channel. This becomes necessary if normal channel selectionwould use a digital input that is already in use as a digital output.
