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Altera_Forum's avatar
Altera_Forum
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15 years ago

ALTGX for A2GX always outputs K28.5- ?!

Hello,

I perform an RTL simulation (ModelSim) of an ALTGX transmitter-only for an Arria II GX. The transmitter is set to take a 20-bit input. I use Basic mode, 4 lanes unbonded. After I release powerdown and resets the proper way (see attachment), the PLL will lock normally.

The problem is that the ALTGX ignores the 20-bit data I feed to its input and goes on outputting over and over K28.5- (0101111100).

Help!

3 Replies

  • Altera_Forum's avatar
    Altera_Forum
    Icon for Honored Contributor rankHonored Contributor
    15 years ago

    The same problem with simulating altgx 3gb/s 1 lane 16bit+8b/10b basic mode transmitter+receiver cyclone iv gx.

    The receiver works fine after correct initialization procedure, transmitter do not. I have added pause, like you, but no success, it is in stuck state.

    The initializing procedure: (timescale = 1ps) 

    initial begin
		gxb_powerdown <= 0;
		pll_areset <= 0;
		rx_analogreset <= 0;
		rx_digitalreset <= 0;
		tx_digitalreset <= 0;
		
	# 10000 gxb_powerdown <= 1;
		pll_areset <= 1;
		rx_analogreset <= 1;
		rx_digitalreset <= 1;
		tx_digitalreset <= 1;
		
	# 1000000	pll_areset <= 0;
		gxb_powerdown <= 0;
		wait( pll_locked) repeat( 300) @ (posedge tx_clkout);
		tx_digitalreset <= 0;
		wait( ~busy) repeat( 3) @ (posedge tx_clkout);
		rx_analogreset <= 0;
		wait( rx_freqlocked)# 4000000 rx_digitalreset <= 0;
	end

    This - "wait( pll_locked) repeat( 300) @ (posedge tx_clkout)" do not help.

    There is no required pause in handbook's description.
  • Altera_Forum's avatar
    Altera_Forum
    Icon for Honored Contributor rankHonored Contributor
    15 years ago

    I have found a solution to my problem. On the contrary to what is told in the A2GX manual (Figure 4-3), tx_digitalreset must NOT be deasserted right after pll_locked goes to 1 but some delay must be added.

    I delayed 16 clocks (@ 100 MHz) tx_digitalreset deassertion after pll_locked goes high. The ALTGX now quits outputting K.28.5- and K.28.6- and starts outputting the real data I am feeding to it.

    Great that I found it, sad that, once again, I'm losing time fixing somebody else's bugs.