The CD54/74HC190 are asynchronously presettable BCD decade counters, whereas the CD54/74HC191 and CD54/74HCT191 are asynchronously presettable binary counters.
Presetting the counter to the number on preset data inputs (A–D) is accomplished by a low asynchronous parallel load (LOAD)\ input. Counting occurs when LOAD\ is high, count enable (CTEN)\ is low, and the down/up (D/U) input is either high for down counting or low for up counting. The counter is decremented or incremented synchronously with the low-to-high transition of the clock.
When an overflow or underflow of the counter occurs, the MAX/MIN output, which is low during counting, goes high and remains high for one clock cycle. This output can be used for look-ahead carry in high-speed cascading (see Figure 1). The MAX/MIN output also initiates the ripple clock (RCO)\ output, which is normally high, goes low and remains low for the low-level portion of the clock pulse. These counters can be cascaded using RCO\ (see Figure 2).
If a decade counter is preset to an illegal state or assumes an illegal state when power is applied, it returns to the normal sequence in one or two counts, as shown in the state diagrams (see Figure 3).
| Typ | Titel | Datum | ||
|---|---|---|---|---|
| * | Data sheet | CD54HC190, CD74HC190, CD54HC191, CD74HC191, CD54HCT191, CD74HCT191 datasheet (Rev. E) | 07 Okt 2003 | |
| Application note | Implications of Slow or Floating CMOS Inputs (Rev. E) | 26 Jul 2021 | ||
| Selection guide | Logic Guide (Rev. AB) | 12 Jun 2017 | ||
| Application note | Understanding and Interpreting Standard-Logic Data Sheets (Rev. C) | 02 Dez 2015 | ||
| User guide | LOGIC Pocket Data Book (Rev. B) | 16 Jan 2007 | ||
| Application note | Semiconductor Packing Material Electrostatic Discharge (ESD) Protection | 08 Jul 2004 | ||
| User guide | Signal Switch Data Book (Rev. A) | 14 Nov 2003 | ||
| Application note | TI IBIS File Creation, Validation, and Distribution Processes | 29 Aug 2002 | ||
| Application note | CMOS Power Consumption and CPD Calculation (Rev. B) | 01 Jun 1997 | ||
| Application note | Designing With Logic (Rev. C) | 01 Jun 1997 | ||
| Application note | SN54/74HCT CMOS Logic Family Applications and Restrictions | 01 Mai 1996 | ||
| Application note | Using High Speed CMOS and Advanced CMOS in Systems With Multiple Vcc | 01 Apr 1996 |
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Das 14-24-LOGIC-EVM-Evaluierungsmodul (EVM) ist für die Unterstützung aller Logikgeräte konzipiert, die sich in einem 14-Pin- bis 24-Pin-D-, DW-, DB-, NS-, PW-, DYY- oder DGV-Gehäuse befinden.
| Gehäuse | Pins | Herunterladen |
|---|---|---|
| PDIP (N) | 16 | Optionen anzeigen |
| SOIC (D) | 16 | Optionen anzeigen |
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