Clocks
116
SPNU503C – March 2018
Copyright © 2018, Texas Instruments Incorporated
Architecture
Table 2-10. Clock Domains (continued)
Clock Domain
Clock
Domain #
Default
Source
Source
Selection
Register
Special Considerations
VCLKA1
4
VCLK
VCLKASRC
• Clock domain dedicated for the CAN controllers: DCAN1, DCAN2,
DCAN3, used for baud-rate generation
• Defaults to VCLK as the source
• Frequency can be as fast as HCLK frequency
• Is disabled via the CDDISx registers bit 4
VCLKA3
10
VCLK
VCLKACON1
• Clock domain dedicated to provide the 48MHz clock to the USB
host controller and device controller
• Defaults to VCLK as the source
• Frequency can be as fast as HCLK frequency
• Is disabled via the CDDISx registers bit 10
VCLKA3_DIVR
10
VCLK
VCLKACON1
• Clock domain dedicated to provide the 12MHz clock to the USB
host controller
• Divided down from the VCLKA3 using the VCLKA3R field of the
VCLKACON1 register at address 0xFFFFE140
• Frequency can be VCLKA3/1, VCLKA3/2, ..., or VCLKA3/8
• Default frequency is VCLKA3/2 and needs to be changed to
VCLKA3/4 to generate the 12MHz clock from the 48MHz VCLKA3
clock
• Is disabled separately via the VCLKACON1 register
VCLKA3_DIV_CDDIS bit, only if the VCLKA3 clock is not disabled
VCLKA4
11
VCLK
VCLKACON1
• Clock domain dedicated for the Ethernet controller (EMAC) when
the TX and RX clocks are internally generated
• Defaults to VCLK as the source
• Frequency can be as fast as HCLK frequency
• Is disabled via the CDDISx registers bit 11
RTICLK
6
VCLK
RCLKSRC
• Clock domain dedicated for timebase generation in the Real-Time
Interrupt (RTI) generation module
• Defaults to VCLK as the source
• If a clock source other than VCLK is selected for RTICLK, then
the RTICLK frequency must be less than or equal to VCLK/3
• Application can ensure this by programming the RTI1DIV field of
the RCLKSRC register, if necessary
• Is disabled via the CDDISx registers bit 6
Each of the control registers indicated in
are defined in
. The AC timing
characteristics for each clock domain are specified in the device datasheet.