The 74161 (common variants 74LS161, 74HC161) is a 74-series logic 4-bit latch and upwards counter. Several discrete logic mappers use it as a latch.
.--\/--. /Clear -o|01 16|-- +5V Clock --|02 15|-- CarryOut D0 --|03 14|-- Q0 D1 --|04 13|-- Q1 D2 --|05 12|-- Q2 D3 --|06 11|-- Q3 CountEnable --|07 10|-- CarryIn Gnd --|08 09|o- /Load `------'
While /Clear is low, Q is reset to 0.
When CountEnable and CarryIn are both high, a low-to-high transition on Clock increases the value of Q by 1, wrapping from 15 to 0.
CarryOut is high when CarryIn is high and Q is 15.
/Load causes Q to be set to the value of D on a low-to-high transition of Clock.
Categories: 7400 series