sawtooth unexpected changes in simulink

Hello everyone, I am trying to create triangular wave in simulink in user defined function:

My code is;

function [s1,s2,s3,s4,g1,g2,g3,g4,g1in,g2in,g3in,g4in]= fcn(sin)
persistent t;
s1=[0];
s2=[0];
s3=[0];
s4=[0];
a=[0];
b=[0];
c=[0];
d=[0];
coder.extrinsic('sawtooth')
if  isempty(t)
t=0;
end

T=0.000001;
Ts=0.000001;
t=t+Ts;

a=sawtooth(2*1000*pi*t,0.5);
s1=a;

b=sawtooth(2*1000*pi*t-pi,0.5)/4;
s2=b+0.25;

c=sawtooth(2*1000*pi*t,0.5)/4;
s3=c-0.25;

d=sawtooth(2*1000*pi*t-pi,0.5)/4;
s4=d-0.75;
end

actually, I am trying to create triangular wave that its freq is 1000 Hz. I could do it with this code, but after 3 or 4 simulation freq of triangular wave is changed itself. Same code same simulink but it is changed

I could not understand that . May u help me ?

thankss