AR# 260: XBLOX 5.x: Implementing DATA_REG in IOB resources
AR# 260
XBLOX 5.x: Implementing DATA_REG in IOB resources
Description
Keywords: XBLOX, data_reg, IOB
Urgency: Standard
General Description:
How do I force DATA_REG to be implemented in an I/O block?
Solution
The following STYLE attributes, new in XACT 5.0, are available on the DATA_REG module to control where the DATA_REG flip-flops are placed.
* STYLE=IOB: Implement as either IFDs or OFDs (input FF or output FF) * STYLE=IFD: Implement as IFDs (input FFs) * STYLE=OFD: Implement as OFDs (output FFs). * STYLE=ILD: Implement as ILDs (level-sensive input latches) * STYLE=CLB: Implement in CLB FFs
If you do not specify a style, XBLOX will select the appropriate style based on how the DATA_REG is connected. For example, in an XC4000, if the DATA_REG is connected to an INPUTS symbol and does not use a clock enable, the DATA_REG will be merged into the input flip-flops. Otherwise, the DATA_REG will use CLB flip-flops.