OrReg8
OrReg8(MCR, MCR_RTS);
OrReg8(MCR, bit);
OrReg8(MCR, LCR_BREAK);
OrReg8(FCR, mask);
void OrReg8(int reg, uint8 value);
ssize_t OrReg8(uint16 address, uint8 data, uint8 mask=0xff);
if (OrReg8(SN9C102_CHIP_CTRL, on ? 0x01 : 0x00) < 0)