83Plus:BCALLs:4CED

Synopsis

Official Name: ClearRow

BCALL Address: 4CED

Clears eight consecutive LCD display drive rows

Inputs

• A = LCD display driver row coordinate (0x80 – 0xBF)

Outputs

• Eight pixel rows cleared
• Driver left in X increment mode (the default)

Destroys

• AF, B, DE

Comments

This routine requires A to be in LCD display driver row (X) coordinates, which have a valid range between 0x80 – 0xBF, with the top pixel row equal to 0x80 and the bottom pixel row equal to 0xBF. Passing in a value for A outside this range will cause unpredictable results and probably a lockup. This routine erases eight consecutive rows, so if you pass in A = 0x88, the 9th – 16th pixel rows from the top of the display are erased. If you pass in a value between 0xB9 – 0xBF, the erased rows wrap back to the top of the display. In normal usage, if you are erasing a line of large text, the A value should be a multiple of 0x08.