SN74HC257 SN74HC253 SN74HC20 SN74HC238 SN74HC237 SN74HC239 SN74HC253-Q1 SN74HC251 SN74HC258 SN74HC21 SN74HC21-Q1 SN74HC240 SN74HC241 SN74HC244 SN74HC244-EP SN74HC244-Q1 SN74HC244A SN74HC245 SN74HC253-EP SN74HC259 SN74HC266 SN74HC27 SN74HC273 SN74HC273-Q1 SN74HC280 SN74HC283