A_RXRDY
while ((KBD->ac_cs & (A_IRQ | A_RXRDY)) != 0)
if ((KBD->ac_cs & (A_IRQ | A_RXRDY)) != 0) {
while ((KBD->ac_cs & (A_IRQ | A_RXRDY)) != 0)
while ((stat & (A_RXRDY | A_OE | A_PE)) != 0) {
while (!((KBD->ac_cs & (A_IRQ | A_RXRDY)) == (A_IRQ | A_RXRDY)))