83Plus:Ports:29

This port only exists as a distinct port on the TI-83 Plus Silver Edition, the TI-84 Plus, and the TI-84 Plus Silver Edition. On the standard TI-83 Plus, it acts as a shadow of port 01.

Synopsis

Port Number: 29h

Function: LCD Delay (6 MHz)

This port removes the amount of delay needed between accesses to the LCD driver by adding a delay to any instruction which reads from or writes to ports 10 or 11, as well as the mirror ports 12 and 13.

Usage

• Bit 0 enables the effects of the flash delay controlled by port 2E.
• Bit 1 enables the effects of the ram delay controlled by port 2E.
• Bits 2-7 control the amount of delay added at specified instructions. To calculate the number of clock cycles added, divide the contents of port 29 by 4 and round off. NOTE: The contents of this port should NOT be less than 0Ch or the LCD driver will no longer respond.

Comments

This port is not available on the normal TI-83+. On the normal TI-83+ this port is a shadow of Port 01h.

Bits 0&1 are reset on the 83+SE and set on the 84+(se).

The effect of this port is only seen if the contents of port 20h equals 00.

As noted above, a delay less than 3 cycles causes LCD outputs to fail. However, it seems that LCD inputs (from any port) will work with a delay of 1 or more. With a delay of 0, both inputs and outputs seem to fail. Is this all a hardware glitch? Who knows.

Credits and Contributions

• Michael Vincent: Documentation as found here.
• James Montelongo: Documentation found at here.