6 CLOCK MANAGEMENT UNIT (CMU)
S1C33L26 TECHNICAL MANUAL
Seiko Epson Corporation
6-13
LCDC Module Clock (LCLK)
6.7.5
LCLK
LCLK_EN
OSC3
LCLKDIV[4:0]
Divider
(1/1–1/32)
7.5.1 LCLK Control Circuit
Figure 6.
The LCLK clock is generated by dividing the OSC3 clock and is supplied the LCD controller (LCDC). The fre-
quency 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]
7.5.1 LCDC Clock (OSC3 Division Ratio) Selections
Table 6.
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 that PCLK2 is required to set the LCDC registers.
In HALT mode, LCLK does not stop if LCLK_EN is set to 1. To stop supplying the clock in HALT mode, LCLK_
EN should be set to 0 before executing the halt instruction.
In SLEEP mode (when the slp instruction is executed), LCLK stops even if LCLK_EN is set 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.
SRAMC and SDRAMC Clock (SDCLK)
6.7.6
SDCLK (to SDRAMC and SRAMC)
SDCLK_EN
SYSCLK
SDCLK (to SDCLK pin)
7.6.1 SDCLK Control Circuit
Figure 6.
The SDCLK clock is used for the SRAMC and SDRAMC. SYSCLK is supplied as SDCLK. SDCLK_EN/CMU_
CLKCTL register is used for clock supply control. The default setting of SDCLK_EN is 1, which enables the clock
supply. Disable the clock supply by setting SDCLK_EN to 0 to reduce current consumption when the external bus
devices (e.g., SRAM and SDRAM) are not used. When using the SDRAMC in double frequency mode (MCLK
: SDCLK = 1 : 2), the SDRAMC operates with SDCLK (Max. 72 MHz) configured to double the frequency of
MCLK (Max. 36 MHz), while the SRAMC operates on the same frequency as MCLK.