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AR# 23026

8.1 System Generator for DSP - How do I use the DSP48 Instruction function for constant block to control the DSP48?


When I use the constant block in System Generator to provide opmode for DSP48, I select DSP48 Instruction type for constant block. However, the output bit width is 11-bit instead of the 7-bit opmode. Why is the ouptut 11 bits? How do I use the output to control the DSP48 block?


The 11-bit output includes opmode(7-bits), substract(1-bit), carry_in(1-bit), and carry_in_sel(2-bits) pins. There are several options for using this 11-bit output: 

- Combine the control bits into a single bus using the "Consolidate control port" option in the DSP48. 

- Use slice block to extract the corresponding bits from the constant block output for each input port. 

- Consider using a normal constant block (non-DSP48 Instruction mode) if you want to control the DSP48 control pins separately.

AR# 23026
Date Created 09/04/2007
Last Updated 05/20/2014
Status Archive
Type General Article