CPU Timer precision - can't find my logic mistake

/*
This example uses the CPU timer to cause an interrupt and to toggle a pin on GPIO12
 */

#include "DSP28x_Project.h"     // Device Headerfile and Examples Include File
__interrupt void timer0_isr(void);

void main(void) {
	
	// Step 1: Setting the PLL, Watchdog, enable peripheral clocks
	InitSysCtrl();

	// Step 2: Initialize your GPIO
	InitGpio();

	// Step 3: Initialize the PIE control registers
//	DINT; // Only necessary here if InitPieCtrl() does not have DINT; included
	InitPieCtrl();

	IER = 0x0000;
	IFR = 0x0000;

	// Step 4: Initialize the PIE vector table to default ISR
	InitPieVectTable();

	// Step 5: Initialize other device peripherals
	// Set GPIO as an output and initialize its state as logic 0
	EALLOW;
	GpioCtrlRegs.GPADIR.bit.GPIO12 = 1;
	EDIS;
	GpioDataRegs.GPACLEAR.bit.GPIO12 = 1;

	// Remap the ISR function to the PIE vector table
	EALLOW;
	PieVectTable.TINT0 = &timer0_isr;
	EDIS;

	// Initializes timer 0 peripherals using the CpuTimers.c function
	InitCpuTimers();
	// Configures CPU timer 0 using the CpuTimers.c function. 150Mhz CPU freq. and 300ns period
	ConfigCpuTimer(&CpuTimer0,150,0.3);

	// Starting the counter and enabling the CPU timer interrupt
	CpuTimer0Regs.TCR.bit.TSS = 0;	// Clears TSS bit and starts CPU timer
	CpuTimer0Regs.TCR.bit.TIE = 1;	// Enables the CPU timer interrupt

	// Enable TINT0 in PIE
//	PieCtrlRegs.PIECTRL.bit.ENPIE = 1;	// Enables PIE vector table. Already enabled in InitPieVectTable();
	PieCtrlRegs.PIEIER1.bit.INTx7 = 1;	// Group 1, bit 7 for timer0
	IER |= M_INT1;						// Sets the interrupt enable bit of group 1
	EINT;								// Enable global interrupts INTM





	for(;;)
	{

	}
}

__interrupt void timer0_isr(void)
{
	// Set GPIO12 during ISR
	GpioDataRegs.GPASET.bit.GPIO12 = 1;

	// Acknowledge interrupt to receive more interrupts from group 1
	PieCtrlRegs.PIEACK.all = PIEACK_GROUP1;
	GpioDataRegs.GPACLEAR.bit.GPIO12 = 1;
}