1 / 11

Programmable Keyboard/Display Interface - 8279

Programmable Keyboard/Display Interface - 8279. 8279 contains the following features:. Simultaneous and independent scanning of a keyboard and refresh of a display, significantly offloading these functions from the microprocessor. Keyboard section: 8-character Keyboard FIFO

Download Presentation

Programmable Keyboard/Display Interface - 8279

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript


  1. Programmable Keyboard/Display Interface - 8279

  2. 8279 contains the following features: • Simultaneous and independent scanning of a keyboard and refresh of a display, • significantly offloading these functions from the microprocessor. Keyboard section: • 8-character Keyboard FIFO • 2-Key Lockout or N-key Rollover with Contact Debounce • Interrupt Output on Key Entry • Programmable Keyboard Scan & Debounce rates Display Section: • Dual 8- or 16-Numeric Display • Single 16-Character Display • Right or Left Entry 16-Byte Display RAM with address auto increment • Programmable display refresh rate Available in VHDL, Verilog, or FPGA-Specific Netlist

  3. PIN DIAGRAM

  4. Pinout Definition 8279 • P A0: Selects data (0) or control/status (1) for reads and writes between micro and 8279. • P BD: Output that blanks the displays. • P CLK: Used internally for timing. Max is 3 MHz. • P CN/ST: Control/strobe, connected to the control key on the keyboard. • P CS: Chip select that enables programming, reading the keyboard, etc. • P DB7-DB0: Consists of bidirectional pins that connect to data bus on micro. • P IRQ: Interrupt request, becomes 1 when a key is pressed, data is available. • P OUT A3-A0/B3-B0: Outputs that sends data to the most significant/least significant nibble of display. • P RD(WR): Connects to micro's IORC or RD signal, reads data/status registers. • P RESET: Connects to system RESET. • P RL7-RL0: Return lines are inputs used to sense key depression in the keyboard matrix. • P Shift: Shift connects to Shift key on keyboard. • P SL3-SL0: Scan line outputs scan both the keyboard and displays

  5. KEYBOARD SECTION • Has eight lines: RL0 to RL7 + two additional lines: CNTL/STB; connected to 8 columns of the keyboard • 2 modes: • 2 key lockout: if two keys are pressed simultaneously only 1st key is recognized • N-key rollover: simultaneous keys are recognized and their codes are stored in internal buffer. • Keyboard section also includes 8X8 FIFO which further consists of eight registers that can store 8 keyboard entries.

  6. SCAN SECTION • Has scan counter and four scan lines: SL0 to SL3 • These are decoded using 4X16 decoder • Further these 16 lines are connected to rows of matrix keyboard and digital drivers of multiplexed display

  7. DISPLAY SECTION • Has 8 output lines divided into 2 groups A0 to A3 and B0 to B3 • These lines can be used as a group of 8 lines or 2 groups of 4 lines each in conjunction to scan lines for display • Display can be blanked by BD line • Includes 16X8 display RAM • MPU can read or write into these registers

  8. MPU INTERFACE SECTION • Includes 8 bidir. Data lines (DB0-DB7), one Interrupt Request (IRQ) and six lines for interfacing, including buffer add line A0 • When A0 is high – control word • When A0 is low – signals are interrupted and they act as data lines • IRQ goes high whenever data entries are stored in FIFO

More Related