逻辑
RS244
This RS244 is an octal non-inverting buffer/driver with 3- state outputs. The 3-state outputs are controlled by the output enable inputs 1OE ̅̅̅̅ and 2OE ̅̅̅̅. A HIGH on OE ̅̅̅̅ causes the outputs to assume a high impedance OFF-state. VCC supporting operating voltage from 1.65 V to 5.5 V. To ensure the high-impedance state during power up or power down, OE ̅̅̅̅ should be tied to VCC through a pullup resistor, the minimum value of the resistor is determined by the current-sinking capability of the driver.
