TMS570LS3137: CAN message transmit interval is varying between two message frames

Hello,

We intended to transfer two message frames with unique11-bit identifier. We are using MB-1 for first frame and MB-2 for second frame.  The software writes two message frames at every 2ms into the MBs using IF1 sequentially as per "Figure 24-7. Data Transfer Between IF1 / IF2 Registers and Message RAM in TRM".

The CAN monitor log below shows that the delay between 2 frames is sometimes ~80us and sometimes ~170us. 

      ID                                    Timestamp

1 1056 8 0 0 0 0 0 0 41 44   0.009990 R
1 1568 8 0 0 0 0 0 0 41 44   0.010070 R    - Diff 80us

1 1056 8 0 0 0 0 0 0 204 55   0.011950 R
1 1568 8 0 0 0 0 0 0 204 55   0.012030 R - Diff 80us

1 1056 8 0 0 0 0 0 0 205 55   0.013910 R
1 1568 8 0 0 0 0 0 0 205 55   0.014080 R - Diff 170us

1 1056 8 0 0 0 0 0 0 206 55   0.015960 R
1 1568 8 0 0 0 0 0 0 206 55   0.016040 R - Diff 80us

1 1056 8 0 0 0 0 0 0 207 55   0.017920 R
1 1568 8 0 0 0 0 0 0 207 55   0.018010 R - Diff 80us

1 1056 8 0 0 0 0 0 0 208 55   0.019880 R
1 1568 8 0 0 0 0 0 0 208 55   0.020050 R - Diff 170us

Could you please suggest what could be causing this behavior.

Thanks,

Jaiganesh