LCD Controller Operation
LCD Controller 8-9
During the same period, the line buffer m ust be filled. The following TDMA duration is how long the DMA
cycle will hold up the bus:
Thus, the percentage of host bus time taken up by the LCD controller’s DMA is PDMA:
8.2.5 Self-Refresh Mode
The LCD driver from Epson was used as a reference for the design of the refresh mode. In self-refresh
mode, the LCD module will update the screen periodically from internal RAM using the LP and FRM
pulse.

8.2.5.1 Entering Self-Refresh Mode

Setting the self-refresh register bit 7 to 1 means that the LSCLK and LD will remain 0 when the end of the
frame is reached. The LP and FRM pulse continue as in normal mode, but there ar e no pulses on either the
LSCLK or LD.

8.2.5.2 Canceling Self-Refresh Mode

Setting the self-refresh register bit 7 to 0 means that the no rmal mode is entered when the end of the frame
is reached. On entering normal mode, data is sent out from the beginning of the page.
T
l1
60 Hz
---------------1
240 lines
----------------------
×=
69.4 µs=
TDMA 320 pixels 2 bits pe r pixel×2clocks×
16.67 MHz 16-bit bus×
-----------------------------------------------------------------------------------------------------=
4.8 µs=
PDMA 4.8‘ µs
69.4‘ µs
---------------------=
6.92‘%=