What you want to do is shift the bits for each byte. Shift left to scroll up, shift right to scroll down.

Scroll up: sutun_reg[i]=sutun_reg[i] << 1

Scroll up: sutun_reg[i]=sutun_reg[i] >> 1

Note that this does NOT carry the bits over, so after doing it 8 times, the display will be blank.

If you want to display to "roll", then you would need to save the MSbit (or LSbit scrolling down) and then make it the LSbit (MSbit for scrolling down)after the shift.

so, here's one way to do that (there is likely a more efficient way).

Code:
temp_byte = sutun_reg[i]
temp_bit = temp_byte.7
temp_byte = temp_byte << 1
temp_byte.0 = temp_bit
sutun_reg[i] = temp_byte