BS1_SEL
if (in_8(&mr->bus_status1) & (BS1_BSY | BS1_SEL)) {
if ((in_8(&mr->bus_status1) & (BS1_BSY | BS1_SEL)) == 0)
if (in_8(&mr->bus_status1) & (BS1_BSY | BS1_SEL)) {
if (in_8(&mr->interrupt) == 0 && (in_8(&mr->bus_status1) & BS1_SEL)
if (in_8(&mr->interrupt) == 0 && (in_8(&mr->bus_status1) & BS1_SEL)