The HCMS-3966 is a step along the trend in the evolution of LED smart displays, designed for a world of programmable microcontrollers where no factor holds more weight than reducing the number of I/O pins needed to control a device. The HCMS-3966 is a 3.3 volt compatible serial display that works much like the earlier HDSP-2xxx devices, in that it has no character driver and data is directly shifted into registers that represent the LEDs in the 5x7 display matrix. Unlike the tedious to control HDSP-2xxx devices, the registers in the HCMS-3966 shift bits in a logical manner from right to left, making it much easier to shift data into the device. Unfortunately the 3966 is a much less TTL friendly device than the HDSP-2xxx; a built in brightness register is set to zero by default, and can only be changed by clocking in the correct serial data word into the appropriate control register. This is one device that can not be clocked and tested manually with pushbuttons.
HCMS-3966 Series Datasheet
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