# 7400-Series Logic ICs Specification ## 1. Overview The **7400-series** is a large family of **digital logic integrated circuits** originally implemented in **TTL (Transistor-Transistor Logic)** and later expanded to include **CMOS-compatible variants**. These devices provide fundamental building blocks such as gates, flip-flops, counters, multiplexers, decoders, and bus transceivers. 7400-series ICs are widely used in **retrocomputing**, **6502/Z80 systems**, **glue logic**, and educational designs. --- ## 2. Logic Families | Family | Technology | Notes | | ------- | ----------------------- | ----------------------- | | 74xx | TTL | Original bipolar TTL | | 74LSxx | Low-power Schottky TTL | Faster, lower power | | 74HCTxx | CMOS (TTL-level inputs) | Ideal for mixed systems | | 74HCxx | CMOS | Wide voltage range | | 74ACTxx | Advanced CMOS TTL-level | Very fast | --- ## 3. Electrical Characteristics (Typical) | Parameter | TTL | CMOS | | ----------------- | ------- | ------------------- | | VCC | 5 V | 2-6 V (5 V typical) | | Input HIGH | ≥ 2.0 V | ≥ 0.7xVCC | | Input LOW | ≤ 0.8 V | ≤ 0.3xVCC | | Fan-out | ~10 | Very high | | Power consumption | Higher | Lower | --- ## 4. Standard Package Types | Package | Pins | Notes | | ------- | ---------- | ------------------- | | DIP | 14, 16, 20 | Breadboard-friendly | | SOIC | 14, 16, 20 | Surface-mount | | TSSOP | 14, 16 | Compact SMT | --- ## 5. Common Logic Categories ### 5.1 Basic Logic Gates | IC | Function | | ---- | ----------------- | | 7400 | Quad 2-input NAND | | 7402 | Quad 2-input NOR | | 7404 | Hex inverter | | 7408 | Quad 2-input AND | | 7432 | Quad 2-input OR | | 7486 | Quad 2-input XOR | --- ### 5.2 Latches and Flip-Flops | IC | Function | | ----- | --------------------- | | 7474 | Dual D-type flip-flop | | 7473 | Dual JK flip-flop | | 7475 | Quad latch | | 74175 | Quad D-type FF | --- ### 5.3 Counters and Registers | IC | Function | | ----- | ------------------------------------- | | 74161 | Synchronous 4-bit counter | | 74163 | Synchronous binary counter | | 74193 | Up/down counter | | 74164 | Serial-in/parallel-out shift register | | 74165 | Parallel-in/serial-out shift register | --- ### 5.4 Decoders and Multiplexers | IC | Function | | ----- | ----------------------- | | 74138 | 3-to-8 decoder | | 74139 | Dual 2-to-4 decoder | | 74151 | 8-to-1 multiplexer | | 74157 | Quad 2-to-1 multiplexer | --- ### 5.5 Bus Interface and Glue Logic | IC | Function | | ----- | ----------------------------------- | | 74244 | Octal buffer / line driver | | 74245 | Octal bidirectional bus transceiver | | 74373 | Octal transparent latch | | 74574 | Octal D-type FF | --- ## 6. Pin Numbering Convention * DIP packages use **counter-clockwise numbering** * Pin 1 identified by notch or dot ```text ________ 1 °| |° 14 2 °| |° 13 3 °| |° 12 4 °| |° 11 5 °| |° 10 6 °| |° 9 7 °|________|° 8 ``` --- ## 7. Power and Ground Pins | Package | VCC | GND | | ------- | --- | --- | | DIP-14 | 14 | 7 | | DIP-16 | 16 | 8 | | DIP-20 | 20 | 10 | --- ## 8. Timing Characteristics (General) | Parameter | TTL | CMOS | | ----------------- | ------- | -------- | | Propagation delay | 5-15 ns | 8-25 ns | | Max frequency | ~25 MHz | ~50+ MHz | --- ## 9. Interfacing Notes * TTL outputs reliably drive TTL inputs * CMOS inputs must not float * Use **74HCT** when interfacing CMOS with TTL signals * Decoupling capacitors (0.1 µF) required per IC --- ## 10. Typical Retrocomputer Applications * Address decoding * Chip-select generation * Bus buffering * Clock gating and control * State machines --- ## 11. Absolute Maximum Ratings (Summary) | Parameter | Rating | | ------------------- | --------------------- | | VCC | -0.5 V to +7.0 V | | Input voltage | -0.5 V to VCC + 0.5 V | | Storage temperature | -65 °C to +150 °C | --- ## 12. References * * * ---