$400F/16399/CIA+15:      CIA Control Register B

   +----------+--------------------------------------------------------+
   | Bit  7   |   Set Alarm/TOD-Clock: 1 = Alarm, 0 = Clock            |
   | Bits 6-5 |   Timer B Mode Select:                                 |
   |          |            00 = Count System 02 Clock Pulses           |
   |          |            01 = Count Positive CNT Transitions         |
   |          |            10 = Count Timer A Underflow Pulses         |
   |          |            11 = Count Timer A Underflows While CNT     |
   | Bit  4   |   Force Load Timer B: 1 = Now! (Write only Strobe Bit) |                      |
   | Bit  3   |   Timer B Run Mode: 1 = One-Shot, 0 = Continuous       |
   | Bit  2   |   Timer B Output Mode to PB7: 1 = Toggle, 0 = Pulse    |
   | Bit  1   |   Timer B Output on PB7: 1 = Yes, 0 = No               |
   | Bit  0   |   Start/Stop Timer B: 1 = Start, 0 = Stop              |
   +----------+--------------------------------------------------------+

   Default Value: $11/17 (%00010001)

ROM-Reference:

 STA $400F  : $CBAD