Article Details

ID: 3310
Case Type: faq
Category: Device Programming
Related To:
Family: MachXO2

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The Transparent Mode command is 0x74, 0x80, 0x00. The always expression is: always @(negedge hard_rst_n,posedge epld_clk_25m) begin if(!hard_rst_n) begin .... reg_en_watchdog<=1'b1; .... else if... .... We can get the initialized value of reg_en_watchdog when hard_rst_n is low in normal user mode. But when we enable transparent configuration mode(I2C port), we can't get initialized value yet even exit the configuration mode with 0x26, 0x00,0x00 command. I have tested the waveform of reg_en_watchdog and hard_rst_n by mapping to unused pins. Please check the reg_en_watchdog&hard_rst.png file. I found the hard_rst_n is tieing to GSR in lmth_lmth.mrp file. I set the GSR as false in strategy---map design---infer GSR and generate JED file again. We can get the initialized value of reg_en_watchdog when hard_rst_n is low both in normal user mode and transparent configuration mode. Would you please help to confirm why GSR is impacted by I2C configuration. Should it be set false for the designs using JTAG/SPI/I2C port to program CPLD?

Based on the TN1246, the transpare mode command will disable the feature of GSR: "Note: Enabling Flash Memory (UFM/Configuration) Interface using Enable Configuration Interface command 0x74 Transparent Mode will temporarily disable certain features of the device including:
  • Power Controller 
  • GSR
  • Hardened User SPI port"

So when you use this command, the feature of GSR will be disabled.
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