Texas Instruments TMS3320C5515 사용자 설명서
System Clock Generator
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1.4.4.5
Clock Configuration Register 1 (CCR1) [1C1Eh]
The clock configuration register 1 (CCR1) is shown in
and described in
.
Figure 1-10. Clock Configuration Register 1 (CCR1) [1C1Eh]
15
1
0
Reserved
SDCLK_EN
R-0
R/W-0
LEGEND: R = Read only; -n = value after reset
Table 1-17. Clock Configuration Register 1 (CCR1) Field Descriptions
Bit
Field
Value
Description
15-1
Reserved
0
Reserved. This bit must be kept as 0 during writes to this register.
0
SDCLK_EN
SDRAM clock enable control. When ON, the EM_SDCLK pin will drive the clock signal at the
SYSCLK frequency if in full_rate mode or at SYSCLK frequency divided by 2 if in half_rate mode.
When OFF, the EM_SDCLK pin will drive low. Transitions from ON to OFF and OFF to ON are not
guaranteed to be glitchless. Therefore, the EMIF should be reset after any change.
SYSCLK frequency if in full_rate mode or at SYSCLK frequency divided by 2 if in half_rate mode.
When OFF, the EM_SDCLK pin will drive low. Transitions from ON to OFF and OFF to ON are not
guaranteed to be glitchless. Therefore, the EMIF should be reset after any change.
0
EM_SDCLK off (default)
1
EM_SDCLK on. This bit must be set to 1 before using SDRAM or mSDRAM.
1.4.4.6
Clock Configuration Register 2 (CCR2) [1C1Fh]
The clock configuration register 2 (CCR2) is shown in
and described in
.
Figure 1-11. Clock Configuration Register 2 (CCR2) [1C1Fh]
15
6
5
4
3
2
1
0
Reserved
SYSCLKSRC
Reserved
CLKSELSTAT
Reserved
SYSCLKSEL
R-0
R-0
R/W-0
R-0
R-0
R/W-0
LEGEND: R/W = Read/Write; R = Read only; -n = value after reset
Table 1-18. Clock Configuration Register 2 (CCR2) Field Descriptions
Bit
Field
Value
Description
15-6
Reserved
0
Reserved.
5-4
SYSCLKSRC
System clock source status bits. These read-only bits reflect the source for the system clock. This
status register exists to indicate that switching from the PLL BYPASS_MODE to the PLL_MODE
was successful or not. Logic exists on the chip to prevent switching to PLL_MODE if the PLL has its
PWRDN bit already asserted. However, this circuit does not protect against asserting the PWRDN
bit after already in PLL_MODE. Therefore, software must ultimately make sure not to do something
that would cause the system clock to be lost.
status register exists to indicate that switching from the PLL BYPASS_MODE to the PLL_MODE
was successful or not. Logic exists on the chip to prevent switching to PLL_MODE if the PLL has its
PWRDN bit already asserted. However, this circuit does not protect against asserting the PWRDN
bit after already in PLL_MODE. Therefore, software must ultimately make sure not to do something
that would cause the system clock to be lost.
0
The system clock generator is in bypass mode; SYSCLK is driven by the RTC oscillator output.
1h
The system clock generator is in PLL mode; the RTC oscillator output provides the input clock.
2h
The system clock generator is in bypass mode; SYSCLK is driven by CLKIN.
3h
The system clock generator is in PLL mode; the CLKIN pin provides the input clock.
3
Reserved
0
Reserved. This bit must be written to be 0.
2
CLKSELSTAT
CLK_SEL pin status bit. This reflects the state of the CLK_SEL pin.
0
CLK_SEL pin is low (RTC input clock selected).
1
CLK_SEL pin is high (CLKIN input clock selected).
1
Reserved
0
Reserved. This bit must be written to be 0.
0
SYSCLKSEL
System clock source select bit. This bit is used to select between the two main clocking modes for
the DSP: bypass and PLL mode. In bypass mode, the DSP clock generator is bypassed and the
system clock is set to either CLKIN or the RTC output (as determined by the CLKSEL pin). In PLL
mode, the system clock is set to the output of the DSP clock generator. Logic in the system clock
generator prevents switching from bypass mode to PLL mode if the PLL is powered down.
the DSP: bypass and PLL mode. In bypass mode, the DSP clock generator is bypassed and the
system clock is set to either CLKIN or the RTC output (as determined by the CLKSEL pin). In PLL
mode, the system clock is set to the output of the DSP clock generator. Logic in the system clock
generator prevents switching from bypass mode to PLL mode if the PLL is powered down.
0
Bypass mode is selected.
1
PLL mode is selected.
32
System Control
SPRUFX5A – October 2010 – Revised November 2010
Copyright © 2010, Texas Instruments Incorporated