74LS603 Memory Refresh Controllers IC (74603) DIP-20 Package

The 74HC194/74HCT194 is a 4-bit bidirectional universal shift register. The synchronous operation of the device is determined by the mode select inputs (S0, S1). In parallel load mode (S0 and S1 HIGH) data appearing on the D0 to D3 inputs, when S0 and S1 are HIGH, is transferred to the Q0 to Q3 outputs. When S0 is HIGH and S1 is LOW data is entered serially via DSL and shifted from left to right; when S0 is LOW and S1 is HIGH data is entered serially via DSR and shifted from right to left. DSR and DSL allow multistage shift right or shift left data transfers without interfering with parallel load operation. If both S0 and S1 are LOW, existing data is retained in a hold mode. Mode select and data inputs are edge-triggered, responding only to the LOW-to-HIGH transition of the clock (CP). Therefore, the only timing restriction is that the mode control and selected data inputs must be stable one set-up time prior to the positive transition of the clock pulse. When LOW, the asynchronous master reset (MR) overrides all other input conditions and forces the Q outputs LOW. Inputs include clamp diodes. This enables the use of current limiting resistors to interface inputs to voltages in excess of VCC.

The 74F251 is a high-speed 8-input digital multiplexer. It provides, in one package, the ability to select one bit of data from up to eight sources. It can be used as a universal function generator to generate any logic function of four variables. Both assertion and negation outputs are provided

Features :-

• Multifunctional Capacity
• On-Chip Select Logic Decoding
• Inverting and Noninverting 3-State Output

The 74HC163; 74HCT163 is a synchronous presettable binary counter with an internal look-head carry. Synchronous operation is provided by having all flip-flops clocked simultaneously on the positive-going edge of the clock (CP). The outputs (Q0 to Q3) of the counters may be preset to a HIGH or LOW. A LOW at the parallel enable input (PE) disables the counting action. It causes the data at the data inputs (D0 to D3) to be loaded into the counter on the positive-going edge of the clock. Preset takes place regardless of the levels at count enable inputs (CEP and CET). A LOW at the master reset input (MR) sets Q0 to Q3 LOW after the next positive-going transition on the clock input (CP). This action occurs regardless of the levels at input pins PE, CET and CEP. This synchronous reset feature enables the designer to modify the maximum count with only one external NAND gate. The look-ahead carry simplifies serial cascading of the counters. Both CEP and CET must be HIGH to count. The CET input is fed forward to enable the terminal count output (TC). The TC output thus enabled will produce a HIGH output pulse of a duration approximately equal to a HIGH output of Q0. This pulse can be used to enable the next cascaded stage. Inputs include clamp diodes. This enables the use of current limiting resistors to interface inputs to voltages in excess of VCC

Features :-

• Complies with JEDEC standard no. 7A
• Input levels:

For 74HC163: CMOS level For 74HCT163: TTL level

• Synchronous counting and loading
• 2 count enable inputs for n-bit cascading
• Synchronous reset
• Positive-edge triggered clock
• ESD protection:

HBM JESD22-A114F exceeds 2 000 V MM JESD22-A115-A exceeds 200 V

• Multiple package options
• Specified from -40 °C to +85 °C and -40 °C to +125 °C

The 74F541 except that the inputs and outputs are on opposite sides of the package (see Connection Diagrams). This pinout arrangement makes these devices especially useful as output ports for microprocessors, allowing ease of layout and greater PC board density

Features :-

• 3-STATE outputs drive bus lines
• Inputs and outputs opposite side of package, allowing easier interface to microprocessors