68k:Ports:600000
From WikiTI
This port controls I/O from pins 99 and 100 on the ASIC. It's used to check battery voltage on all calcs, and to control LCD contrast on the TI-92.
| Bit 7 | Pin 100 output enable (keep =0) |
| Bit 6 | Pin 99 output enable (keep =0) |
| Bit 5 | Data to pin 100 (TI-92: used for LSB of LCD contrast) |
| Bit 4 | Data to pin 99 (not used) |
| Bit 3 | Data from pin 100 (not used) |
| Bit 2 | Data from pin 99 (1 if batt. voltage is above trigger level (see 600018) |
| Bits 1-0 | not used |
