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Drive segment display and control keyboard chip CH452 |
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| 1. Introduction |
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CH452 is driving segment display and controlling the keyboard scan chip. CH452 set clock oscillate circuit internally to dynamically drive 8-bit segment display or 64-bit LEDs. CH452 has BCD encode, glitter,shift,segment bit addressing,light pole encode and other function. Besides, CH452 can scan 64-key keyboard. CH452 can exchange data with MCU via 4-wire or 2-wire serial interface which can layer connect. Furthermore, CH452 can supply power on reset signal for MCU. |
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| 2.1. Display drive |
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●Set current drive layer internally, segment current is no less than 20mA, word current is no less than 100mA .
●Dynamically display scan control, directly drive 8-bitnumeric LEDs, 64 LEDs or 64-layer light pole.
●Select no-encode manner or BCD encode manner for corresponding segment and data bit.
●BCD encode supports one self-defined BCD code to display a particular character.
●Data in segment display move to left, right and left cycle, right cycle.
●The data in each segment display is glitter controlled separate, the slow and quick glitter speed is selectable.
●Any segment is searched address by bit, control each LED or every segment in segment display shine and un-shine independently.
●64-layer light pole encode, display light pole value via light pole composed by 64 LEDs.
●Scan limit control, supports 1 to 8 segments displaying, distribute scan time for active segment display.
●Word drive output polarity is optional, convenient to enlarge drive voltage and current external. |
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| 2.2. Keyboard control |
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●Set 64-key keyboard controller internal basic on 88 matrix keyboard scan.
●Set pull-down resistor on key-press status and set getting rid of jitter circuit internal.
●Key-press interrupt, low-level active output or low-level pulse output is optional.
●Supplies flag bit for release key-press, key-press is pressed or releaseed can be queried.
●Support key-press woke-up, CH452 can be woke up be some key-presses from low-power status. |
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| 2.3. External interface |
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●For the identical chip, high-speed 4-wire serial interface or economical 2-wire interface is selectable.
●For 4-wire serial: supports many chips to layer connect, the clock speed is varies from 0 to 2MHz, compatible with CH451.
●For 4-wire serial: together use DIN and DCLK signal wire with other interface circuit to save pin.
●For 2-wire serial: supports two CH452 to parallel connect (set each address by ADDR pin level)
●For 2-wire serial: clock speed is varies from 500Hz to 200Hz,compatible with 2-wire I2C bus to save pin.
●Set power-up reset internal, supplies high-level activate and low-level activate reset output for MCU. |
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| 2.4. Other option |
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●Set clock oscillate circuit internal, no need external to supply clock or connect to oscillate equipment,resist disturb ability is stronger.
●Supports low-power sleep to economize power, be woke up by key-press or command operation.
●Supports 3V~5V power.
●Two kinds packages: SOP28 and DIP24S, pins are compatible with CH451. |
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| 3. Package |
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