26 LCD CONTROLLER (LCDC)
26-6
Seiko Epson Corporation
S1C33L26 TECHNICAL MANUAL
Setting the LCDC Clock
26.4.2
The LCDC operates with the LCLK, BCLK, and PCLK2 clocks supplied from the CMU. For controlling the
clocks, see the “Clock Management Unit (CMU)” chapter.
LCLK
This is the LCDC operating clock (pixel clock) generated by dividing the OSC3 clock. The frequency divider
generates 32 kinds of clocks from OSC3/1 to OSC3/32. Select a division ratio according to the frame rate using
LCLKDIV[4:0]/CMU_LCLKDIV register.
f
LCLK
Frame rate = ————— [Hz]
HT
×
VT
f
LCLK
: LCLK frequency
HT: Horizontal total period (horizontal panel size + horizontal non-display period) [pixels]
VT: Vertical total period (vertical panel size + vertical non-display period) [lines]
4.2.1 LCDC Clock (OSC3 Division Ratio) Selections
Table 26.
LCLKDIV[4:0]
Division ratio (OSC3/n)
LCLKDIV[4:0]
Division ratio (OSC3/n)
0x1f
1/32
0xf
1/16
0x1e
1/31
0xe
1/15
0x1d
1/30
0xd
1/14
0x1c
1/29
0xc
1/13
0x1b
1/28
0xb
1/12
0x1a
1/27
0xa
1/11
0x19
1/26
0x9
1/10
0x18
1/25
0x8
1/9
0x17
1/24
0x7
1/8
0x16
1/23
0x6
1/7
0x15
1/22
0x5
1/6
0x14
1/21
0x4
1/5
0x13
1/20
0x3
1/4
0x12
1/19
0x2
1/3
0x11
1/18
0x1
1/2
0x10
1/17
0x0
1/1
(Default: 0x7)
LCLK_EN/CMU_CLKCTL register is used for clock supply control (default: off). Before using the LCDC, set
LCLK_EN to 1.
Note: Disable LCLK supply (LCLK_EN = 0) when changing the clock division ratio using LCLKDIV[4:0]
or before executing the slp instruction.
BCLK
This clock is required for the LCDC to access the VRAM. BCLK can be stopped in HALT mode using BCLK_
EN/CMU_CLKCTL register.
PCLK2
This clock is required for accessing the LCDC registers. PCLK2 can be stopped using PCLK2_EN/CMU_
CLKCTL register.