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| author | David Shah <davey1576@gmail.com> | 2017-12-06 17:48:15 +0000 |
|---|---|---|
| committer | David Shah <davey1576@gmail.com> | 2018-01-16 15:17:20 +0000 |
| commit | 77eafa89b4b9d8852071cc68298f92465311470b (patch) | |
| tree | 711acedb69f15874930ceb7dae9b03dd9019608a /docs | |
| parent | 9e81ac7786d7633b7d1c204318f1559bca300643 (diff) | |
| download | icestorm-77eafa89b4b9d8852071cc68298f92465311470b.tar.gz icestorm-77eafa89b4b9d8852071cc68298f92465311470b.tar.bz2 icestorm-77eafa89b4b9d8852071cc68298f92465311470b.zip | |
HFOSC trimming info
Diffstat (limited to 'docs')
| -rw-r--r-- | docs/ultraplus.html | 8 |
1 files changed, 8 insertions, 0 deletions
diff --git a/docs/ultraplus.html b/docs/ultraplus.html index 694b82d..dac648a 100644 --- a/docs/ultraplus.html +++ b/docs/ultraplus.html @@ -205,6 +205,14 @@ The <span style="font-family:monospace">CLKHF</span> output of SB_HFOSC is conne <p>Configuration bit <span style="font-family:monospace">CLKHF_DIV[1]</span> maps to DSP1 tile (0, 16) config bit <span style="font-family:monospace">CBIT_4</span>, and <span style="font-family:monospace">CLKHF_DIV[0]</span> maps to DSP1 tile (0, 16) config bit <span style="font-family:monospace">CBIT_3</span>.</p> +<p>There is also an undocumented trimming function of the HFOSC, using the ports <span style="font-family:monospace">TRIM0</span> through <span style="font-family:monospace">TRIM9</span>. This can only be accessed directly in iCECUBE if you modify the standard cell library. However + if you set the attribute <span style="font-family:monospace">VPP_2V5_TO_1P8V</span> (which itself is not that well documented either) to 1 on the top level module, then the configuration bit + <span style="font-family:monospace">CBIT_5</span> of (0, 16) is set; and <span style="font-family:monospace">TRIM8</span> and <span style="font-family:monospace">TRIM4</span> are connected to + the same net as <span style="font-family:monospace">CLKHFPU</span>.</p> +<p><span style="font-family:monospace">TRIM[3:0]</span> connect to <span style="font-family:monospace">(25, 28, lutff_[7:4]/in_0)</span> and <span style="font-family:monospace">TRIM[9:4]</span> + connect to <span style="font-family:monospace">(25, 29, lutff_[5:0]/in_3)</span>. <span style="font-family:monospace">CBIT_5</span> of (0, 16) must be set to enable trimming. The trim range +on the device used for testing was from 30.1 to 75.9 MHz. TRIM9 seemed to have no effect, the other inputs could broadly be considered to form a binary word, however it appeared neither linear +nor even monotonic.</p> <h3>SB_LFOSC</h3> <p>The <span style="font-family:monospace">CLKLFPU</span> input connects through IPConnect tile (25, 29) input <span style="font-family:monospace">lutff_0/in_1</span>; and the <span style="font-family:monospace">CLKLFEN</span> input connects through input <span style="font-family:monospace">lutff_7/in_3</span> of the same tile.<br/> |