Intel P8275 Gain Differential Amplifier 27V 1mA 80KHz IC DIP-40
The 8275 is a single-chip programmable CRT controller designed to interface raster-scan CRT displays with Intel microcomputer systems. It buffers display information from main memory, manages row and character timing, and generates raster timing (horizontal and vertical retrace). By providing two row buffers and programmable counters, the device refreshes the screen while minimizing CPU and DMA overhead, enabling flexible character and screen formats.
The chip supports 1–80 characters per row and 1–64 rows per frame, with programmable lines per character (1–16) and underline placement. It decodes character and field attributes (blink, highlight, reverse video, underline, plus two general-purpose outputs) and provides special control codes (end-of-row, end-of-screen) to reduce memory and DMA traffic. Two 80-character row buffers and two 16-character FIFOs support visible and invisible field-attribute modes.
The 8275 generates DMA requests for burst transfers (1–8 characters per burst) with programmable burst spacing, and signals interrupts at frame boundaries. It exposes a 3-state bidirectional data bus, command/parameter/status registers, light-pen inputs and registers, and cursor control with four cursor formats. The chip requires external dot-timing/dot-clock logic and typically interfaces with standard character generator ROMs; its programmability reduces external hardware and software complexity.
Features:
- Programmable screen and character formats (1–80 characters/row, 1–64 rows/frame).
- Two independent row buffers (dual row buffering).
- Six independent visual field attributes (blink, highlight, reverse video, underline, GPA0, GPA1).
- Eleven visual character attributes and special control codes (end-of-row/screen, stop DMA variants).
- Programmable DMA burst mode (1–8 characters per burst) with adjustable spacing.
- Cursor control (4 cursor types: blinking/non-blinking underline or reverse-video block).
- Light-pen detection with position registers.
- Two 16-character FIFOs for invisible field-attribute mode.
- 3-state bidirectional 8-bit data bus and standard control register set.
- Single +5 V supply; available in a 40-pin package.
Specifications:
| Parameter / Item | Value / Range (from datasheet) |
|---|---|
| Device: | Intel 8275 Programmable CRT Controller |
| Package: | 40-pin package (DIP-40) |
| Supply: | +5 V (Vcc = 5V ±5%) |
| Ambient operating temp: | 0°C to 70°C (under bias) |
| Storage temp: | −65°C to +150°C |
| Voltage on any pin (abs max): | −0.5 V to +11 V |
| Power dissipation (max): | 1 Watt |
| Typical supply current (Ice / Vee supply): | ~160 mA (DC characteristic; datasheet lists 160 mA) |
| Logic thresholds: | VIL max = 0.8 V; VIH min = 2.0 V |
| Output levels: | VOL max ≈ 0.45 V (IOL = 2.2 mA) VOH min = 2.4 V (IOH = −400 µA) |
| Capacitive loads: | CIN ≈ 10 pF CIO (I/O) ≈ 20 pF (unmeasured pins to Vss) |
| Timing highlights: | Character code output delay tcc ≥ 150 ns HRTe, LCO, ATR, VRTC delays listed (see datasheet) |
| FIFO depth: | Two FIFOs, 16 characters each (7-bit wide) |
Pin Configurations:
Applications:
- Microcomputer CRT display interface.
- Raster-scan CRT controller in video terminals.
- Character generator interface systems.
- Light-pen interactive display systems.
- Multi-row buffered display controllers.
Package Contents:
- 1x Intel P8275 Gain Differential Amplifier 27V 1mA 80KHz IC DIP-40