Description:
The MM74C911 display controller is an interface element with memory that drives a 4-digit, 8-segment LED display. The MM74C911 allows individual control of any segment in the 4-digit display. The number of segments per digit can be expanded without any external components. For example, two MM74C911’s can be cascaded to drive a 16-segment alpha-numeric display. The display controllers receive data information through 8 data lines a, b…DP, and digit information through 2 address inputs K1 and K2. The input data is written into the register selected by the address information when CHIP ENABLE, CE, and WRITE ENABLE, WE, are LOW and is latched when either CE or WE return HIGH. Data hold time is not required. A self-contained internal oscillator sequentially presents the stored data to high drive (100 mA typ.) 3-STATE output drivers which directly drive the LED display. The drivers are active when the control pin labeled SEGMENT OUTPUT ENABLE, SOE, is LOW and go into 3-STATE when SOE is HIGH. This feature allows for duty cycle brightness control, or for disabling the output drive for power conservation. The MM74C911 display controller is an interface element with memory that drives a 4-digit, 8-segment LED display. The MM74C911 allows individual control of any segment in the 4-digit display. The number of segments per digit can be expanded without any external components. For example, two MM74C911’s can be cascaded to drive a 16-segment alpha-numeric display. The display controllers receive data information through 8 data lines a, b…DP, and digit information through 2 address inputs K1 and K2. The input data is written into the register selected by the address information when CHIP ENABLE, CE, and WRITE ENABLE, WE, are LOW and is latched when either CE or WE return HIGH. Data hold time is not required. A self-contained internal oscillator sequentially presents the stored data to high drive (100 mA typ.) 3-STATE output drivers which directly drive the LED display. The drivers are active when the control pin labeled SEGMENT OUTPUT ENABLE, SOE, is LOW and go into 3-STATE when SOE is HIGH. This feature allows for duty cycle brightness control, or for disabling the output drive for power conservation.
The digit outputs directly drive the base of the digit transistor when the control pin labeled DIGIT INPUT OUTPUT, DIO, is LOW. When DIO is HIGH, the digit lines turn into inputs and the internal scanning multiplexer is disabled. When any digit line is forced HIGH by an external device, usually another MM74C911, the data information for that digit is presented to the output. In this manner, 16-segment alpha-numeric displays, 24- or 32-segment displays, or an array of discrete LED's can be controlled by the simple cascading of expandable segment display controllers. All inputs except digit inputs are TTL compatible and do not clamp input voltages above VCC.
Features :
■ Direct segment drive (100 mA typ.) 3-STATE
■ 4 registers addressed like RAM
■ Internal oscillator and scanning circuit
■ Direct base drive to digit transistor
■ Segment expandability without external components
■ TTL compatible inputs
■ Power saver mode—5 µW (typ.)
(Picture:Pinout / Diagram)
