74161: Difference between revisions

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m (Created page with 'The '''74161''' is a 74-series logic 4-bit latch and upwards counter. All(?) known uses of it inside cartridges just use it as a latch. == 74161 Pinout == <pre> .--...')
 
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The '''74161''' is a 74-series logic 4-bit latch and upwards counter. All(?) known uses of it inside cartridges just use it as a latch.
The '''74161''' (common variants 74LS161, 74HC161) is a 74-series logic 4-bit latch and upwards counter.
Several discrete logic [[mapper]]s use it as a latch.
== 74161 Pinout ==
== 74161 Pinout ==
<pre>
              .--\/--.
              .--\/--.
      /Clear -o|01  16|-- +5V
    /Clear - |01  16| - +5V
      Clock --|02  15|-- CarryOut
      Clock - |02  15| - CarryOut
          D0 --|03  14|-- Q0
        D0 - |03  14| - Q0
          D1 --|04  13|-- Q1
        D1 - |04  13| - Q1
          D2 --|05  12|-- Q2
        D2 - |05  12| - Q2
          D3 --|06  11|-- Q3
        D3 - |06  11| - Q3
CountEnable --|07  10|-- CarryIn
CountEnable - |07  10| - CarryIn
        Gnd --|08  09|o- /Load
        Gnd - |08  09| - /Load
              `------'
              `------'</pre>
== Signal descriptions ==
== Signal descriptions ==
While /Clear is low, Q is reset to 0.
While /Clear is low, Q is reset to 0.
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/Load causes Q to be set to the value of D on a low-to-high transition of Clock.
/Load causes Q to be set to the value of D on a low-to-high transition of Clock.
[[Category:7400 series|161]]

Revision as of 04:25, 31 January 2013

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.

74161 Pinout

              .--\/--.
     /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
              `------'

Signal descriptions

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.