________________ ________________ ___________________
| | | | | |
| ATTiny85 (MCU) |-----| 74HC595 (FLAG) |-----| 74HC595 (ADDRESS) |
|________________| |________________| |___________________|
| | | | |
| | | +-/7/-+ +--- TO MCU
|__|__|___________|________ |
|E RW RS A0-A6 A7|-*
| HD44780U (LCD controller) |
|___________________________|
- PB0 - LCD busy pin and the MSB of the LCD bus.
- PB1 - Serial out to the shift registers.
- PB2 - Clock for serial input on the shift registers.
- PB3 - Clock for the outputs on the shift registers.
- PB4 - PS/2 clock.
- PB5 - Reset pin, left open for programming.