I have attached some test code I used to perfect monochrome scrolling and the use of PROGMEM. The output routine is currently configured for testing on the Rainbowduino but was intended for MAX7219 chips. The final code went into a 16x8 MAX7219 driven matrix and would support 24x8 as it stands and *maybe 56x8 with minimal modification. *I say maybe because I'm not sure how fast it would scroll.
ScrollTest3.ino (13.8 KB)