6.逻辑符号(Logic Symbol) 低电平有效 Active Low NAND gate RS-Latch 无O 高电平有效 Active High NOR gate RS-Latch 6. 逻辑符号( Logic Symbol ) S R Q Q Q Q & & R S NAND gate RS－Latch Q Q ≥1 S R ≥1 S R Q Q NOR gate RS－Latch 低电平有效 Active Low 无 高电平有效 Active High