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Overview
6.1
Overview
This device requires two primary reference clocks:
•
One reference clock is required for the phase-locked loop controllers (PLLCs)
•
One reference clock is required for the real-time clock (RTC) module.
These reference clocks may be sourced from either a crystal input or by an external oscillator. For detailed
specifications on clock frequency and voltage requirements, see the device-specific data manual.
In addition to the reference clocks required for the PLLCs and RTC module, some peripherals, such as the
USB, may also require an input reference clock to be supplied. All possible input clocks are described in
. The CPU and the majority of the device peripherals operate at fixed ratios of the primary
system/ARM clock frequency, as listed in
. However, there are two system clock domains that do
not require a fixed ratio to the ARM, these are PLL0_SYSCLK3 and PLL0_SYSCLK7.
shows
the clocking architecture.
Table 6-1. Device Clock Inputs
Peripheral
Input Clock Signal Name
Oscillator/PLL
OSCIN
RTC
RTC_XI
JTAG
TCK, RTCK
EMAC RMII
RMII_MHZ_50_CLK
EMAC MII
MII_TXCLK, MII_RXCLK
USB2.0
USB_REFCLKIN
I2C0
I2C0_SCL
Timers
TM64Pn_IN12
SPIs
SPIn_CLK
McASP0
ACLKR, AHCLKR, ACLKX, AHCLKX
Table 6-2. System Clock Domains
Fixed Ratio to
Default Ratio to
CPU/Device Peripherals
System Clock Domain
ARM Clock Required?
ARM Clock
ARM RAM/ROM, On-chip RAM, UART0, EDMA, SPI0,
PLL0_SYSCLK2
Yes
1:2
MMC/SD0, DDR2/mDDR (bus ports), USB2.0
EMIFA
PLL0_SYSCLK3
No
1:3
System configuration (SYSCFG), GPIO, PLLCs, PSCs,
PLL0_SYSCLK4
Yes
1:4
EMAC/MDIO, ARM INTC
ARM
PLL0_SYSCLK6
Yes
1:1
EMAC RMII clock
PLL0_SYSCLK7
No
1:6
I2C0, Timer64P0/P1, RTC, USB2.0 PHY, McASP0
PLL0_AUXCLK
Not Applicable
Not Applicable
serial clock
DDR2/mDDR PHY
PLL1_SYSCLK1
Not Applicable
Not Applicable
PLL0 input reference clock
PLL1_SYSCLK3
Not Applicable
Not Applicable
(not configured by default)
UART1/2, Timer64P2/3, McASP0, SPI1
ASYNC3
Not Applicable
Not Applicable
60
Device Clocking
SPRUGX5A
–
May 2011
Copyright
©
2011, Texas Instruments Incorporated
Содержание AM1802
Страница 1: ...AM1802 ARM Microprocessor System Reference Guide Literature Number SPRUGX5A May 2011 ...
Страница 2: ...2 SPRUGX5A May 2011 Submit Documentation Feedback Copyright 2011 Texas Instruments Incorporated ...
Страница 30: ...30 ARM Subsystem SPRUGX5A May 2011 Submit Documentation Feedback Copyright 2011 Texas Instruments Incorporated ...
Страница 144: ...144 Power Management SPRUGX5A May 2011 Submit Documentation Feedback Copyright 2011 Texas Instruments Incorporated ...