Clocks
115
SPNU503C – March 2018
Copyright © 2018, Texas Instruments Incorporated
Architecture
2.4.1.2
Checking for Valid Clock Sources
The application can check whether a clock source is valid or not by checking the corresponding bit to be
set in the Clock Source Valid Status (CSVSTAT) register. For example, the application can check if bit 1 in
CSVSTAT is set before using the output of PLL1 as the source for any clock domain.
NOTE:
The clock sources LF LPO, EXTCLKIN1, and EXTCLKIN2 have no validity check. These
clock sources are considered to be always valid and are available for use by a clock domain
as soon as they are enabled. The application must ensure that a valid clock signal is present
on the EXTCLKINx inputs before enabling these clock sources.
2.4.2 Clock Domains
The clocking on this device is divided into multiple clock domains for flexibility in control as well as clock
source selection. There are 10 clock domains on this device. Each of these are described in
Table 2-10. Clock Domains
Clock Domain
Clock
Domain #
Default
Source
Source
Selection
Register
Special Considerations
GCLK
0
OSCIN
GHVSRC
• Clock domain used by one of the two Cortex-R4F CPUs operating
in lock-step
• Always the same frequency as HCLK
• In phase with HCLK
• Is disabled separately from HCLK via the CDDISx registers bit 0
• Can be divided by 1 up to 8 when running CPU selftest (LBIST)
using the CLKDIV field of the STCCLKDIV register at address
0xFFFFE108
GCLK2
0
OSCIN
GHVSRC
• Clock domain used by the second Cortex-R4F CPU operating in
lock-step
• Always the same frequency as GCLK
• 2 cycles delayed from GCLK
• Is disabled along with GCLK
• Gets divided by the same divider setting as that for GCLK when
running CPU selftest (LBIST)
HCLK
1
OSCIN
GHVSRC
• Clock domain used by the high-speed system modules: Flash
memory interfaces, TCRAM interface, Error Signaling Module
(ESM), DMA
• Is disabled via the CDDISx registers bit 1
VCLK
2
OSCIN
GHVSRC
• Clock domain used by some system modules (VIM), peripheral
modules accessed via the Peripheral Central Resource (PCR)
controller, and all other register interfaces also accessed via the
PCR
• Divided down from HCLK
• Can be HCLK/1, HCLK/2,... or HCLK/16
• Is disabled separately from HCLK via the CDDISx registers bit 2
VCLK2
3
OSCIN
GHVSRC
• Clock domain used by the timer modules: N2HET1, N2HET2 and
the dedicated transfer units: HTU1, HTU2
• Divided down from HCLK
• Can be HCLK/1, HCLK/2,... or HCLK/16
• Frequency must be an integer multiple of VCLK frequency
• Is disabled separately from HCLK via the CDDISx registers bit 3
VCLK3
8
OSCIN
GHVSRC
• Clock domain used for EMAC, USB and EMIF slave interfaces
• Divided down from HCLK
• Can be HCLK/1, HCLK/2,... or HCLK/16
• Is disabled separately from HCLK via the CDDISx registers bit 8