BMI                    BMI Branch on result minus                     BMI

  Operation:  Branch on N = 1                           N V - B D I Z C
                                                        . . . . . . . .

  +----------------+-----------------------+---------+---------+----------+
  | Addressing Mode| Assembly Language Form| OP CODE |No. Bytes|No. Cycles|
  +----------------+-----------------------+---------+---------+----------+
  |  Relative      |   BMI $FFFF           |   $30   |    2    |    2*    |
  +----------------+-----------------------+---------+---------+----------+
  * Add 1 if branch occurs to same page.
  * Add 2 if branch occurs to different page (see explanation).

What it does: Branches up to 127 bytes forward or 128 bytes backward from its own address if the negative (N) flag is set. In effect, it branches if the seventh bit has been set by the most recent event: LDA #150 or LDA #128 would set the seventh bit. These actions would set the N flag, signifying that a minus number is present if you are using signed arithmetic or that there is a shifted character (or a BASIC keyword) if you are thinking of a byte in terms of the ASCII code.

Major uses: Testing for BASIC keywords, shifted ASCII, or graphics symbols. Testing for + or - in signed arithmetic.