SLAU847D October 2022 – May 2024 MSPM0L1105 , MSPM0L1106 , MSPM0L1227 , MSPM0L1228 , MSPM0L1228-Q1 , MSPM0L1303 , MSPM0L1304 , MSPM0L1304-Q1 , MSPM0L1305 , MSPM0L1305-Q1 , MSPM0L1306 , MSPM0L1306-Q1 , MSPM0L1343 , MSPM0L1344 , MSPM0L1345 , MSPM0L1346 , MSPM0L2227 , MSPM0L2228 , MSPM0L2228-Q1
LCD segments need to be refreshed at a certain rate which is known as the frame rate. Typically, frame rates are between 30Hz and 100Hz. In order to generate the waveforms at the required rate, we need to make use of the below clocking circuit shown in the diagram to generate the CLKLCD and CLKFRAME. In addition to this, the charge pump (CLKCP) and boost circuitry (CLKVBST) operation is also supported. The segment blinking is supported by the CLKBLK.
The following table gives a description of the various clocks in the diagram and how the clock frequency is being derived.
Clock | Description | Equation | |
---|---|---|---|
CLKLCD | This clock is used to generate analog mux controls and also to read from LCDMx and LCDBMx memories and drive the common and segment pins. One LCD frame equals 2 × (LCDMX + 1) CLKLCD cycles. | fclklcd = fclklfclk/((LCDCTL0.LCDDIVx+1)×(MUXDIVIDER)) | |
LCDMXx | MUXDIVIDER | ||
0 | 64 | ||
1 | 32 | ||
2 | 16 | ||
3 | 16 | ||
4 | 12 | ||
5 | 8 | ||
6 | 8 | ||
7 | 8 | ||
CLKFRAME | Defines the duration of one LCD frame | fclkframe = fclklcd/((LCDCTL0.LCDMXx+1)×2) | |
CLKBLK | Clock used to flash the segments on and off when blinking is enabled. Segments are turned off when CLKBLK is 0. | fclkblk = fclkframe/2LCDBLKPREx+1 | |
CLKCP | Used to generate 4 phase clocks to charge pump, when charge pump is enabled. | fclkcp = fclklfclk/(LCDVCTL.LCDCPFSELx+1) | |
CLKVBST | Used to boost the voltage on control signals used to control the switches. | Same as LFCLK |
MMR Field | Value |
---|---|
LCDMXx | 2(3-Mux mode) |
LCDBLKPREx | 2(/8)- > 4 frames on and 4 frames off |
The following figure shows the relationship between CLKLCD, CLKFRAME ,and CLKBLK for the configuration in the table above