TMS320F2808: Problems with IQNsinPU function on TMS320F2808

Hello,

I have tried to use _IQ16sinPU function from the C28x IQmath Library

for the sine wave generation on TMS320F2808. I used following code:

static unsigned short frequency = 32767;
static unsigned short delta_phase = 0; 
static long int accumulator = 0; 
static long int u_a = 0; 

// 273 ~ 2*pi*50/12000*1/(2*pi)*65536
// frequency is for setting the desired output frequency, 50 Hz ~ 32767
delta_phase = ((((unsigned long)frequency)*273) >> 15);  
accumulator += delta_phase; 
accumulator &= 0xFFFF; 
u_a = _IQ16sinPU(accumulator);

My problem is that the output of _IQ16sinPU function is in interval <-65536, +65536> according to following graph.

.

Based on the documentation http://www.ti.com/lit/sw/sprc990/sprc990.pdf (page 10) I expected that the values should be in interval

<-32768, +32768>. Please can anybody tell me what could be wrong? There is graph's configuration menu below. Thanks in advance.