S-function level 2 -workspace dimension

Dear Sir/Madam,

I want only single data at each time, but the system gave me four values at a single time, what is wrong it? I am using S-function level 2.

function SetInpPortDims(block, idx, fd) block.InputPort(1).Dimensions = 4; block.InputPort(2).Dimensions = 4; block.InputPort(3).Dimensions = 4;

function SetOutPortDims(block, idx, fd) block.OutputPort(1).Dimensions = 4;

My Simulink system is as shown in http://imgur.com/uQAbK3w

I got this http://imgur.com/XyM0KR5

but what I want is,at t=0, data=20,at t=1, data=20.1,at t=2, data=20.2,at t=3, data=20.2,

If I change the dimension from 4 to 1, I got this error code "Level-2 MATLAB S-Function cannot use 'set default dimension function'."

[want2know]

anyone please?