These devices consist of bus-transceiver circuits with 3-state or open-collector outputs, D-type flip-flops, and control circuitry arranged for multiplexed transmission of data directly from the data bus or from the internal storage 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 octal bus transceivers and registers.

Output-enable () and direction-control (DIR) inputs control the transceiver functions. In the transceiver mode, data present at the high-impedance port may be stored in either or both registers.

The select-control (SAB and SBA) inputs can multiplex stored and real-time (transparent mode)

data. The circuitry used for select control eliminates the typical decoding glitch that occurs in a multiplexer during the transition between stored and real-time data. DIR determines which bus receives data when is low. In the isolation mode ( high), A data may be stored in one register and/or B data may be stored in the other register.

When an output function is disabled, the input function is still enabled and can be used to store and transmit data. Only one of the two buses, A or B, may be driven at a time.

The -1 version of the SN74ALS646A is identical to the standard version, except that the recommended maximum I_OL in the -1 version is increased to 48 mA. There are no -1 versions of the SN54ALS646, SN54ALS648, or SN74ALS648A.

The SN54ALS646, SN54ALS648, and SN54AS646 are characterized for operation over the full military temperature range of -55°C to 125°C. The SN74ALS646A, SN74ALS648A, SN74AS646, and SN74AS648 are characterized for operation from 0°C to 70°C.

• Independent Registers for A and B Buses
• Multiplexed Real-Time and Stored Data
• Choice of True or Inverting Data Paths
• Choice of 3-State or Open-Collector Outputs
• Package Options Include Plastic Small-Outline (DW) Packages, Ceramic Chip Carriers (FK), and Standard Plastic (NT) and Ceramic (JT) 300-mil DIPs

• Technology Family
• ALS
• Supply voltage (Min) (V)
• 4.5
• Supply voltage (Max) (V)
• 5.5
• Number of channels (#)
• 8
• IOL (Max) (mA)
• 24
• IOH (Max) (mA)
• -15
• ICC (Max) (uA)
• 88000
• Input type
• Bipolar
• Output type
• 3-State
• Features
• Very high speed (tpd 5-10ns)
• Rating
• Military

SN54ALS648的完整型号有：5962-9052301LA、SNJ54ALS648JT，以下是这些产品的关键参数及官网采购报价：

5962-9052301LA，工作温度：-55 to 125，封装：CDIP (JT)-24，包装数量MPQ：1个，MSL 等级/回流焊峰值温度：N/A for Pkg Type，引脚镀层/焊球材料：SNPB，TI官网5962-9052301LA的批量USD价格：30.773（1000+）

SNJ54ALS648JT，工作温度：-55 to 125，封装：CDIP (JT)-24，包装数量MPQ：1个，MSL 等级/回流焊峰值温度：N/A for Pkg Type，引脚镀层/焊球材料：SNPB，TI官网SNJ54ALS648JT的批量USD价格：30.773（1000+）

5962-9052301LA，工作温度：-55 to 125，封装：CDIP (JT)-24，包装数量MPQ：1个，MSL 等级/回流焊峰值温度：N/A for Pkg Type，引脚镀层/焊球材料：SNPB，TI官网5962-9052301LA的批量USD价格：30.773（1000+）

SNJ54ALS648JT，工作温度：-55 to 125，封装：CDIP (JT)-24，包装数量MPQ：1个，MSL 等级/回流焊峰值温度：N/A for Pkg Type，引脚镀层/焊球材料：SNPB，TI官网SNJ54ALS648JT的批量USD价格：30.773（1000+）