Migrating to the MityDSP-L138F-A7¶

As described in PCN20211118000, the MityDSP-L138F SOM will be largely unavailable after January of 2022 due to the lack of availability of the Xilinx Spartan-6 FPGA devices. Moving forward, Xilinx has provided guidance that Spartan-6 designs should be updated to use a 7-series FPGA device.

In order to support our users and mitigate as much impact as possible, Critical Link has designed a new variant of the SOM to utilize an Artix-7 FPGA in place of the Spartan-6 FPGA. The SOM is the MityDSP-L138F-A7.

Users with existing designs of the MityDSP-L138F that are planning to migrate to the MityDSP-L138F-A7 variant are encouraged to review this page for useful information and guidance for the port.

Step 1. Review PCN20211118000¶

PCN20211118000 provides a high level summary of the major considerations of the migration.

Step 2. Evaluate the Mechanical Fit¶

While PCN20211118000 mentions that no major mechanical impacts are expected, it has been determined that there is a slight (0.1 mm) clearance increase necessary in the region shown in the figure below in order to support additional capacitors needed for the Artix-7 core voltage power supply. A copy of the current STEP model is available for customers wishing to check for any clearance issues. Critical Link has examined several designs and no issues have been seen with regards to the clearance, the risk is quite low but should be checked.

Step 3. Check for LVDS_33 IO standard¶

As mentioned in the PCN, the Artix-7 FPGA does not support the LVDS_33 IO standard (LVDS input or output on a bank using 3.3V for VCCIO). If your design is leveraging the LVDS_33 standard, you will need to update your carrier card to either:

• Use 2.5V as your bank VCCIO standard
• Move the LVDS pins to a bank with 2.5V VCCIO available
• consider external terminations as per Xilinx Answer Record 43989

Step 4. Check IO standards on pins 143,145,147,149¶

The 2 FPGA IO pair (4 IO pins) on the edge connector located on pins 143,145,147,149 are now assigned to the other bank grouping on the FPGA. If you used 2 different Voltage levels on VCCIO_0 and VCCIO_1 (pins 197/199 and pins 198/200) on your existing design, then you will need to modify your carrier card to support an updated voltage standard or re-assign the pin locations.

Step 5. Port your project to Xilinx Vivado¶

This page includes a zip file, mitydsp-l138f-a7_refproject.zip, that includes the basic constraints file and reference project to build the example Industrial IO board FPGA image as well as defines all of the FPGA ball connections to the edge connector and the OMAP-L138F part.

The reference Vivado project may be built by running the following command in the "build_A7" directory:

vivado -mode batch -source ../script/gen_project.tcl -tclargs --mdk_dir "../MDK/fpga" --part "xc7a15tcsg324-2" 

If you are interested in a build for the 50 KLE density, change the part number to xc7a50tcsg324-2. NOTE: source code for several of the commonly used FPGA cores are included in the MDK folder to support project ports that used Critical Link provided core IP netlists in the past. Some of the cores leverage FPGA FIFOs from the ISE core generator tool. These FIFOs will need to be rebuilt.

Step 6. Port your software¶

The EMIFA interface VHDL code for the MItyDSP-L138F-A7 should follow the same basic protocol and timing standards as for the original MityDSP-L138F design. It should therefor be possible to make an Artix-7 FPGA image that is fully compatible with existing MityDSP-L138F ARM/DSP software. Minimal software impact is anticipated.

For customers that need to support both the Artix-7 and Spartan-6 designs in the field and would like to know which part is deployed, reading the factory configuration I2C EEPROM will provide a unique FPGA part number as well as an updated Part Number field. These fields are assigned as follows:

FPGA Type Code	Model Number Code	Fpga Density
0	X	None
1	F	Spartan-6 6SLX9
2	G	Spartan-6 6SLX16
3	H	Spartan-6 6SLX25
4	I	Spartan-6 6SLX45
11 New	J	Artix-7 XC7A15
12 New	K	Artix-7 XC7A25
13 New	L	Artix-7 XC7A35
14 New	M	Artix-7 XC7A50

New MODEL Code	Artix-7 Density
L138-FJ-326-RC	XC7A15
L138-DJ-325-RI	XC7A15
L138-FM-336-RL	XC7A50
L138-DM-336-RI	XC7A50