Clear_x_b_a ($F552)

This routine sets the block of memory pointed to by the X register to the A register. The B register specifies the number of bytes to be 'filled'.

ENTRY:

A-reg = byte to be stored

B-reg = number of bytes to clear ($00 = 256)

X-reg points to start of memory block to clear

EXIT:

B-reg = $00

Source