Two seven-segment displays were provided to display TOWRP numbers (either currently controlling or currently available) as well as the morale value of a controlled TOWRP. To save output pins on the E128, each seven-segment display was controlled via a shift register connected to the synchronous serial subsystem of the E128. Both shift registers shared the same data line, but had separate slave select lines, and clock lines modulated by those slave select lines, in order to enable the transmission of data to only one shift register at a time without changing the data on the other shift register (if desired, both shift registers could be updated with the same data simultaneously by raising both slave select lines.) Data on the shift registers was used to enable N-channel MOSFETs to pull the individual segments of the seven-segment displays to ground to turn them on, as specified by the seven-segment display design. The seven-segment displays were run at 8 V and 36 mA (using 220 Ω resistors), as requested by the seven-segment displays’ datasheet; however, the shift registers and MOSFETs were run at the standard 5 V in order to enable the selection of standard logic-level MOSFETs.