8x4 Bicolor LED Matrix Question

Other Hardware LEDs and Multiplexing
11

Ah, ok ... I believe I understand now. So, using CrossRoads' matrix example above, if I wanted all LEDs to be green except, say, the top-right LED (DIG6/SEGA[SEGF]), I would need to write to all eight registers as follows:

digitalWrite(ssPin, LOW);
SPI.transfer(0);
SPI.transfer(0b00001111);
SPI.transfer(1);
SPI.transfer(0b00001111);
SPI.transfer(2);
SPI.transfer(0b00001111);
SPI.transfer(3);
SPI.transfer(0b00001111);
SPI.transfer(4);
SPI.transfer(0b00001111);
SPI.transfer(5);
SPI.transfer(0b00001111);
SPI.transfer(6);
SPI.transfer(0b10000111);
SPI.transfer(7);
SPI.transfer(0b00001111);
digitalWrite(ssPin, HIGH);

Does that look to be correct? That's what I figured it should be, assuming I understood you correctly.

One last thing, does the 7219 save the last instructions in its registers/bits and display that until the next round of data? That's to say, if new data is provided, for example, to make the red LED green again and a different one red in a separate register, would I need to reissue all eight register instructions again or only the two that are being changed?

I may just be starting to understand this stuff. Still a loooong way to go though.

Thanks!