programmers_guide.md

Programmer's Guide

To start pattern generation, the register interface of the pattern generator HWIP should be properly initialized and configured.

The guide that follows provides instructions for configuring Channel 0. To configure Channel 1, use the registers with the "CH1" suffix, instead of the "CH0" registers.

To configure a single channel:

1. Before configuration, disable the desired channel by clearing the enable bit, CTRL.ENABLE_CH0.
2. Set the polarity bit, CTRL.POLARITY_CH0, to determine the desired clock phase. For either channel, a zero in the polarity bit indicates that the channel clock line (pcl) should start low, and the channel data line pda transitions on every falling edge of pcl. A one in the polarity bit inverts the pcl clock so that it starts high and pda transitions on the rising edge. The following waveform illustrates the effect of the POLARITY bit. Here both channels are configured for simultaneous pattern generation, but the two channels are configured for opposite polarities.

{signal: [
  {name: 'CTRL.ENABLE_CH0', wave: 'lh......'},
  {name: 'CTRL.POLARITY_CH0 (default: low)', wave: '0.......'},
  {name: 'pcl0_tx', wave: '0.hlhlhl'},
  {name: 'pda0_tx', wave: 'x3.3.3.3', data: 'DATA[0] DATA[1] DATA[2]'},
  {name: 'CTRL.POLARITY_CH1 (high)', wave: '1.......'},
  {name: 'pcl1_tx', wave: '1.lhlhlh'},
  {name: 'pda1_tx', wave: 'x5.5.5.5', data: 'DATA[0] DATA[1] DATA[2]'},
],
  head: {text: 'Effect of the Polarity Registers',tick:0}}

3. Program the length of the seed pattern using the length field, SIZE.LEN_CH0. Note that since the allowed seed length ranges from 1-64, the value of this field should be one less than the pattern length. For example, to generate a 16-bit pattern, a value of 15 should be written to the field SIZE.LEN_CH0.
4. Program the seed pattern (between 1 and 64 bits in length) using the multi-register DATA_CH0_0 and DATA_CH0_1. The first 32 bits to be transmitted are programmed into the lower half of the multi-register (i.e. DATA_CH0_0), and the latter 32 bits are programmed into the upper half of the multi-register (i.e. DATA_CH0_1).
5. Program the clock divider ratio using the register PREDIV_CH0.CLK_RATIO. The resulting clock frequency will be slower than the input I/O clock by a ratio of 2×(CLK_RATIO+1): $$f_{pclx}=\frac{f_\textrm{I/O clk}}{2(\textrm{CLK_RATIO}+1)}$$
6. Program the desired number of pattern repetitions using the repetition field SIZE.REPS_CH0. Note that since the allowed number of pattern repetitions ranges from 1-1024, the value of this field should be one less than the desired repetition count. For example, to send a pattern 30 times, a value of 29 should be written into the field SIZE.REPS_CH0.
7. Finally, to start the pattern set the CTRL.ENABLE_CH0. To start both channel patterns at the same time, configure both channels then simultaneously assert both the CTRL.ENABLE_CH0 and CTRL.ENABLE_CH1 bits in the same register access.

Using the inactive level feature

By default, the pcl and pda outputs are zero when pattgen is inactive (i.e., when pattgen is disabled or after it has sent all data bits). Using the CSR bits CTRL.INACTIVE_LEVEL_PCL and CTRL.INACTIVE_LEVEL_PDA (one pair of bits for channel 0, the other pair for channel 1), one can set either pcl or pda or both to one when pattgen is inactive. The value of the output changes when these CSR fields are set, as the following example shows:

{signal: [
  {name: 'CTRL.ENABLE',             wave: '0..|1.........|0', node: '....e'},
  {name: 'CTRL.POLARITY',           wave: '0..|..........|.'},
  {name: 'CTRL.INACTIVE_LEVEL_PDA', wave: '01.|..........|.', node: '.a'},
  {name: 'CTRL.INACTIVE_LEVEL_PCL', wave: '01.|..........|.', node: '.c'},
  {name: 'data',                    wave: 'x..|.3.4.5.6.x|.', node: '.....f', data: "[0]=1'b0 [1]=1'b1 [2]=1'b0 [3]=1'b1"},
  {name: 'pda',                     wave: '0.1|.0.1.0.1..|.', node: '..b...'},
  {name: 'pcl',                     wave: '0.1|.01010101.|.', node: '..d..'},
],
  edge: ['a~b', 'c~d', 'e~f']
}

Device Interface Functions (DIFs)

• Device Interface Functions