Connection:MOSI pin: from the mcu to shift register's data pin (pin1+2 on HC164 and pin 14 on HC595). LCD's RS pin tied to this line as well.SCK pin: from the mcu to shift register's serial clock pin (pin 8 on HC164 and pin 11 on HC595)Enable pin: from the mcu to the lcd.
Advantages over other 3-wire solutions:1) It allows 8-bit as well as 4-bit mode.2) It uses no parts other than the shift register.3) It allows HC164 as well as HC595.
What about the RCK line (pin 12) on the HC595?
QuoteWhat about the RCK line (pin 12) on the HC595?Connect it to the Enable line: those people who designed HD44780 are incredibly smart and with tons of foresight,
The low level LCD driver uses 28 words of program memory and is isochronous.
With delays for the RC tau of 3.3 microseconds, it takes precisely 83.75 microseconds to send each byte to the LCD.