TXE8124 supports bus hold (bus-keeper) function on all input I/Os which is very useful when the system has to go into low-power or standby state as external pull-up or pull-down correponding to the low-power state are no longer required. By default the feature is disabled and must be enabled through software programming.

On enabling the bus hold feature, the I/O holds the last known active level on the I/O. If the external device drives a logic 1, TXE8124 activates the internal bus hold pull-up. When the controller goes into low-power state making its output pins high-impedance, the internal bus hold pull-up holds the I/O high, thus avoiding a floating input. The same happens when the external device is drives a logic 0, with the TXE8124 activating the internal bus hold pull-down. This also ensures that the TXE8124 does not generate an interrupt due to noise on the floating inputs, as the device is held in the last known state.

When the bus hold feature is enabled, the external driver must ensure that the current sink or source (indicated by the + or - sign on the specification) due to leakage or other circuits on the board must meet the sustaining or override current. As an example, if the bus hold is activated in high state, then the external devices on the line must not source current from TXE8124 that exceeds the I_BHH(MAX) limit. If the limit is exceeded, the voltage may drop below the V_IL(MAX) on the corresponding port pin and trigger the bus-hold pull-down. Similalry, if the bus-hold has to be overriden, then the external devices must be able to sink I_BHO(MIN) current from the TXE8124, to ensure that the device releases the bus-hold.

The software must ensure that the pull-up or pull-down selection must not be used along with the bus-hold feature to avoid additional leakage current in the device.