static READ16_HANDLER( exterm_input_port_1_r ) { return exterm_trackball_port_r(space, 1, mem_mask); }
static READ16_HANDLER( exterm_input_port_0_r ) { return exterm_trackball_port_r(0, mem_mask); }
static READ16_HANDLER( exterm_input_port_1_r ) { return exterm_trackball_port_r(space, 1, mem_mask); }
static READ16_HANDLER( exterm_input_port_0_r ) { return exterm_trackball_port_r(0, mem_mask); }