Update the timer interrupt formula. Update Note 4 for configTIMER_PRE…

…SCALE in README.md

portable/CCRH/F1Kx/README.md

@@ -25,6 +25,7 @@ The test project can be found [here](https://github.com/FreeRTOS/FreeRTOS-Commun
    2. `Channel 0` and address `0xFFFEEC00` are used as default configuration for configIPIR_CHANNEL and configEXCLUSIVE_ADDRESS, in case of resource confliction other channel/address can be used. (2)
    3. The minimal stack size (configMINIMAL_STACK_SIZE) must be included the reserved memory for nested interrupt. This formula can be referred: `(task_context_size) * (1 + configMAX_INT_NESTING) + Stack_depth_of_taskcode`
    In which, `task_context_size` is calculated as `36*4bytes = 144bytes` (when FPU enabled) or `34*4bytes = 136` (when FPU disabled), configMAX_INT_NESTING is 02 as default.
+   4. `configTIMER_PRESCALE`: This value is required in order to correctly configure clock for `CPUCLK_L`. Refer to HWUM at `Table 44.22` for `option byte`: If the user sets the option byte `CKDIVMD to 1`, then `configTIMER_PRESCALE = 4`. Otherwise, if `CKDIVMD is set to 0`, then `configTIMER_PRESCALE = 2`.
 
 (1)  This is applicable for F1KH-D8 with SMP only.
 

portable/CCRH/F1Kx/port.c

@@ -638,8 +638,10 @@ static void prvSetupTimerInterrupt( void )
     *pulOSTMIntReg = ( portINT_PROCESSING_ENABLED | portINT_DIRECT_VECTOR | portINT_PRIORITY_LEVEL14 );
 
     /* Set OSTM0 control setting */
-    *( ( volatile uint32_t * ) portOSTM0CTL_ADDR ) = ( portOSTM_MODE_INTERVAL_TIMER | portOSTM_START_INTERRUPT_DISABLE );
-    *( ( volatile uint32_t * ) portOSTM0CMP_ADDR ) = ( configCPU_CLOCK_HZ / configTICK_RATE_HZ / 2 ) - 1;
+    *( ( volatile uint32_t * ) portOSTM0CTL_ADDR ) =
+        ( portOSTM_MODE_INTERVAL_TIMER | portOSTM_START_INTERRUPT_DISABLE );
+    *( ( volatile uint32_t * ) portOSTM0CMP_ADDR ) =
+        ( ( configCPU_CLOCK_HZ / configTIMER_PRESCALE ) / configTICK_RATE_HZ ) - 1;
 
     /* Enable OSTM0 operation */
     *( ( volatile uint32_t * ) portOSTM0TS_ADDR ) = portOSTM_COUNTER_START;