Difference between revisions of "83Plus:Ports:11"

Revision as of 08:24, 26 May 2007

Synopsis

Port Number: 11h

Function: LCD Data Port

This port transfers data to and from the LCD driver's internal RAM.

Read Values

• The byte at the current location in RAM. Each bit corresponds to one pixel.

NOTE: When the LCD is first turned on (eg, after a removing ALL batteries from the calculator including the backup one) or after the location pointer is changed via the command port, the contents of the LCD's output register will be invalid. Since the output register is only updated on a data read, an extra dummy read is required before you will be able read what is at the new location. This is not required when the location pointer is updated by the auto-increment/decrement.

Write Values

• Sets the byte at the current RAM location. Each bit corresponds to one pixel.

Comments

In 6-bit transfer mode, only bits 0~5 have any significance.

The RAM location affected can be changed through the command port. The location will also automatically change according to the auto-increment or auto-decrement mode as set in the command port. As with sending commands, you must wait a full LCD Cycle (10 microseconds) between reads and writes.

Example

 ;Cause all the pixels at the current location to be black.
 ld a, 0FFh
 out (11h), a
 push hl
 push de
 pop de
 pop hl
 nop
 ;And turn them back off.
 xor a
 out (11h), a

See Also

• Port 10 - LCD command port
• LCD driver datasheet