The 68901 ``MultiFunction peripheral'' device is on the CPU node to provide the console serial line, and the Wanda timer. It also gives some general I/O lines, a ``watch dog'' reset line and a spare timer. Four of the I/O lines are used, two for LEDs and two for the reset reason, table 13 shows the gpio use. Note that the port defaults to all inputs on reset.
The 68901 timer crystal is 2.4576MHz. The inputs to timer A and B are selectable by links, and the output of timer B may be connected to cause the card to reset. Table 14 summarises the timer use.
The 68901 is the only device on the cpu IRQ line, and expects the 68k interrupt response. This is provided using the ``IACK'' access address. Reading from this address causes the IACK strobe rather than CS. The 68901 will then provide the reset vector formed as given in the data sheet. Warning when the 68901 is not interrupting it will not respond to a read of this location. Currently the machine will hang if such an access is attempted - a patch will probably be done to make the access return with bogus data.
