The ’HCT646 devices consist of bus-transceiver circuits with 3-state outputs, D-type flip-flops, and control circuitry arranged for multiplexed transmission of data directly from the input bus or from the internal registers. Data on the A or B bus is clocked into the registers on the low-to-high transition of the appropriate clock (CLKAB or CLKBA) input. Figure 1 illustrates the four fundamental bus-management functions that can be performed with the ’HCT646 devices.
Output-enable (OE)\ and direction-control (DIR) inputs control the transceiver functions. In the transceiver mode, data present at the high-impedance port can be stored in either or both registers.
The select-control (SAB and SBA) inputs can multiplex stored and real-time (transparent mode) data. DIR determines which bus receives data when OE\ is active (low). In the isolation mode (OE\ high), A data can be stored in one register and/or B data can be stored in the other register.
When an output function is disabled, the input function still is enabled and can be used to store data. Only one of the two buses, A or B, can be driven at a time.
To ensure the high-impedance state during power up or power down, OE\ should be tied to VCC through a pullup resistor; the minimum value of the resistor is determined by the current-sinking capability of the driver.
| Typ | Titel | Datum | ||
|---|---|---|---|---|
| * | Data sheet | SN54HCT646, SN74HCT646 datasheet (Rev. C) | 18 Mär 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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