SN74HC148

@@ -0,0 +1,60 @@+# SN74HC148++**Texas Instruments** · 8-to-3 priority encoder · SOIC-16++An 8-to-3 line priority encoder in high-speed CMOS, SOIC-16, the inverse of a decoder. It takes eight active-low inputs and outputs the 3-bit binary number of the highest-numbered one that is active, ignoring lower ones (the priority part). That turns a bank of buttons, interrupt lines, or switches into a compact binary code a microcontroller can read on three pins. Enable-in (EI), enable-out (EO), and group-select (GS) let you cascade two devices into a 16-to-4 encoder. Runs 2-6 V. The KiCad 74LS148 symbol shipped here is pin-identical.++## Pinout++| Pin | Name | Type | Function |+|---|---|---|---|+| 1 | 4 | input | Active-low data input 4. Requests encoding of octal value 4 when asserted (LOW). |+| 2 | 5 | input | Active-low data input 5. Requests encoding of octal value 5 when asserted (LOW). |+| 3 | 6 | input | Active-low data input 6. Requests encoding of octal value 6 when asserted (LOW). |+| 4 | 7 | input | Active-low data input 7 (highest priority). Requests encoding of octal value 7 when asserted (LOW). |+| 5 | EI | input | Active-low enable input. All outputs are forced to their inactive (HIGH) state when EI is HIGH; encoding is enabled when EI is LOW. Used for cascading multiple stages. |+| 6 | A2 | output | Active-low encoded output bit 2 (MSB of the 3-bit octal code). Drives ±4 mA at Vcc = 5 V. |+| 7 | A1 | output | Active-low encoded output bit 1. Drives ±4 mA at Vcc = 5 V. |+| 8 | GND | power_in | Ground reference (0 V). |+| 9 | A0 | output | Active-low encoded output bit 0 (LSB of the 3-bit octal code). Drives ±4 mA at Vcc = 5 V. |+| 10 | 0 | input | Active-low data input 0 (lowest priority). Requests encoding of octal value 0 when asserted (LOW) and no higher-numbered input is active. |+| 11 | 1 | input | Active-low data input 1. Requests encoding of octal value 1 when asserted (LOW). |+| 12 | 2 | input | Active-low data input 2. Requests encoding of octal value 2 when asserted (LOW). |+| 13 | 3 | input | Active-low data input 3. Requests encoding of octal value 3 when asserted (LOW). |+| 14 | GS | output | Active-low group-select output. Goes LOW whenever any data input (0-7) is active and EI is LOW, indicating that a valid encoded value is present on A0-A2. |+| 15 | EO | output | Active-low enable output. Goes LOW when EI is LOW and no data input is asserted, signaling downstream cascaded encoders that they may drive the outputs. |+| 16 | VCC | power_in | Positive supply, 2 V to 6 V (5 V nominal). Icc max 80 µA. |++## Key specifications++| Parameter | Value |+|---|---|+| Type | 8-to-3 priority encoder |+| Inputs | 8 active-low (0-7) |+| Outputs | 3-bit binary (A0-A2, active-low) |+| Priority | highest active input wins |+| Cascade | EI / EO / GS pins |+| Logic family | HC (high-speed CMOS) |+| Supply voltage | 2-6 V |+| Package | SOIC-16 |++## Ordering variants++- `SN74HC148D (SOIC-16, tube)`+- `SN74HC148DR (SOIC-16, tape & reel)`++## CAD (KiCad official)++- Symbol: `74xx:74LS148 (pin-compatible with 74HC148)`+- Footprint: `Package_SO:SOIC-16_3.9x9.9mm_P1.27mm`+- 3D model: SOIC-16 (KiCad packages3D)++## Provenance++Data extracted from the manufacturer datasheet, not a distributor listing:++- **Datasheet:** [Texas Instruments datasheet](https://www.ti.com/lit/ds/symlink/sn74hc148.pdf) (25 pp, sha256 `ca65b15c3841afab`, retrieved 2026-08-17, tier: manufacturer)+- **Extractor:** `ds2sf` (Claude). Every pin and dimension is cited to a datasheet page; it refuses to fabricate.+- **CAD:** KiCad official libraries (CC-BY-SA 4.0).++[Datasheet PDF](docs/sn74hc148-datasheet.pdf)

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