VII LCD CONTROLLER BLOCK: LCD CONTROLLER
7.If necessary, select the pixel clock frequency for use in portrait mode by using the PMODCLK[1:0] (D[1:0])/portrait mode register (0x39FFFB). Note that, in alternate portrait mode, the pixel clock frequency is halved compared to that in landscape mode, without specifically changing register settings. Therefore, the frame rate must be reviewed, including resetting of the
Table 2.15 Clock Settings for Alternate Portrait Mode
PMODCLK1 | PMODCLK0 | Pixel clock PCLK | Memory clock MCLK |
0 | 0 | CLK/2 | CLK |
0 | 1 | CLK/2 | CLK |
1 | 0 | CLK/4 | CLK/2 |
1 | 1 | CLK/8 | CLK/4 |
CLK denotes the LCDC clock selected using the LCLKSEL[2:0] (D[2:0])/FIFO control register (0x39FFF4).
8.Set alternate portrait mode.
PMODEN
Upon completion of the above setting, the display mode is switched to portrait mode.
When using an LCD panel with a vertical resolution of less than 256 lines, a virtual screen similar to the one in default portrait mode can be configured. The screen can be panned or scrolled by setting a value (including offset) in the line byte count register, and then controlling the screen 1 start address register.
In alternate portrait mode, the screen can be scrolled in the vertical direction one line at a time.
Comparison of portrait modes
The differences between default portrait mode and alternate portrait mode are summarized in Table 2.16.
Table 2.16 Differences between Portrait Modes
Parameter | Default portrait mode | Alternate portrait mode |
Display | Sufficient display memory must be available | If a virtual screen is not being configured, no |
memory | so that the horizontal size following rotation | memory area other than that for the image |
| is the original value to the power of 2. In | size is required. |
| many cases, that value differs from the LCD |
|
| panel size, and an unused area occurs |
|
| unless the value is used as a virtual screen. |
|
| To display a 240 ⋅ |
|
| rotating a 320 ⋅ |
|
| degrees, for example, as much display |
|
| memory as for a horizontal size of 28 = 256 |
|
| pixels must be available. For |
|
| this is normally 320 ⋅ 240 = 76,800 bytes, |
|
| but for portrait display, 256 ⋅ 320 = 81,920 |
|
| bytes are required. |
|
Clock | MCLK for display memory access and the | MCLK must be twice as fast as PCLK. |
| pixel clock PCLK for LCD display may be | PCLK cannot be set to above 12.5 MHz. |
| used at the same speed. |
|
Power | The LCD controller can operate at low | A greater amount of power than in default |
consumption | power. | portrait mode is consumed. |
Vertical scroll | Can be scrolled two lines at a time. | Can be scrolled one line at a time. |
Display | Standard performance. | Higher performance than default portrait |
performance |
| mode. |
EPSON | S1C33L03 FUNCTION PART |