User Manual
100
Rev. 1.1
2019-03-18
TLE984xQX
Microcontroller with LIN and Power Switches for Automotive Applications
System Control Unit - Digital Modules (SCU-DM)
7.3.4
Clock Control Unit
The Clock Control Unit (CCU) receives the clock from the PLL
f
PLL
, the external input clock
f
OSC
, the internal
input clock
f
INTOSC
, or the low-precision input clock
f
LP_CLK
. The system frequency is derived from one of these
clock sources.
Figure 29 Clock Inputs to Clock Control Unit
The CCU generates all necessary clock signals within the microcontroller from the system clock. It consists of:
• Clock slow down circuitry
• Centralized enable/disable circuit for clock control
In normal running mode, the main module frequencies (synchronous unless otherwise stated) are as follows:
• System frequency,
f
SYS
= up to 25 MHz or 40 MHz (product variant dependant) (measurement interface
clock MI_CLK is derived from this clock)
• CPU clock (CCLK, SCLK) = up to 25 MHz or 40 MHz (product variant dependant) (divide-down of NVM access
clock)
• NVM access clock (NVMACCCLK) = up to 25 MHz or 40 MHz (product variant dependant)
• Peripheral clock (PCLK, PCLK2, NVMCLK) = up to 25 MHz or 40 MHz (product variant dependant) (equals
CPU clock; must be same or higher)
• TFILT_CLK: for digital filtering in analog peripherals, e.g. for comparators. Should be configured to be at 2
MHz (as close as possible).
Some peripherals are clocked by PCLK, others clocked by PCLK2 and the NVM is clocked by both NVMCLK and
NVMACCCLK. During normal running mode, PCLK = PCLK2 = NVMCLK = CCLK. On wake-up from power-down
mode, PCLK2 is restored similarly like NVMCLK, whereas PCLK is restored only after PLL is locked.
For optimized NVM access (read/write) with reduced wait state(s) and with respect to system requirements on
CPU operational frequency, bit field NVMCLKFAC is provided for setting the frequency factor between the NVM
access clock NVMACCCLK and the CPU clock CCLK.
For the slow down mode, the operating frequency is reduced using the slow down circuitry with clock divider
setting at the bit field CLKREL. Bit field CLKREL is only effective when slow down mode is enabled via SFR bit
PMCON0.SD bit. Note that the slow down setting of bit field CLKREL correspondingly reduces the NVMACCCLK
clock. Slow down setting does not influence the erase and write cycles for the NVM.
Peripherals UART1, UART2, T2 and T21 and are not influenced by CLKREL and either not by NVMCLKFAC,
to allow functional LIN communication in slow down mode.
CCU_block
M
U
X
CCU
SCU_SYSCON0.
SYSCLKSEL
f
SYS
f
LP_CLK
f
INTOSC
f
OSC
f
PLL