SM501_DC_CRT_CONTROL_SEL
ctrl &= SM501_DC_CRT_CONTROL_SEL;
ctrl |= SM501_DC_CRT_CONTROL_SEL;
ctrl &= ~SM501_DC_CRT_CONTROL_SEL;
ctrl |= SM501_DC_CRT_CONTROL_SEL;
ctrl &= ~SM501_DC_CRT_CONTROL_SEL;
SM501_DC_CRT_CONTROL_SEL)
SM501_DC_CRT_CONTROL_SEL |
if ((control & SM501_DC_CRT_CONTROL_SEL) == 0) {
control |= SM501_DC_CRT_CONTROL_SEL; /* CRT displays CRT data */