Configuration workflow

The typical workflow of the GTM configuration tool starts with the configuration of the Cluster Clock Management Unit (CCM). The following configuration options are available for CCM:

Enablement of all the clusters.
Division of the input clock source.

The input clock source of the CCM is the global clock, which can be configured via the Clocks tool. The GTM IP is divided into clusters, each cluster having its own clock source which can be used to control the available submodules. A change of the cluster divider would trigger a change in all the dependent modules. For example, cluster 0 clock is used as a clock source for the Clock Management Unit (CMU). Therefore, the change of the cluster 0 clock divider would trigger a change in the CMU input clock source, which in turn would affect I/O submodules such as ATOM and TOM. All the available use-cases make use of cluster 0 as their clock source. The enablement of a cluster clock source is done by selecting a divider from its associated combo-box. While the divider can be set to either 1 or 2, the current GTM code generation driver supports only a division by 2.


Figure 1. GTM Tool Overview

The next step is to configure the CMU according to the requirements. The following configuration options are available for CMU:

Custom division ratio can be achieved via the nominator/denominator settings.
Enablement of all the CMU channels.
Enablement of the CMU fixed clock source.
Custom divider for each CMU channel.

The global clock source of the CMU is the cluster 0 clock, configured in the previous step via the Cluster Clock Management Unit. The frequency of the CMU global clock can be configured by changing the Global Clock Numerator and Denominator fields.

The input clock source of the CMU is divided by the following ratio:

The ratio of these two fields must be a number in the interval (0, 1], otherwise a problem would be signaled.

Channels 0-7 of the CMU can be enabled and used as a fixed clock source or as an input clock source for the ATOM channels. The CMU FX (fixed) clock source can be enabled and used as a source for the TOM channels. The fixed clock source is set by default to the CMU global clock frequency and can be changed to any of the enabled CMU channels. Additionally, the CMU channels’ output frequency can be changed by changing the value of the Clock Divider Count.

The equation used to determine the output frequency of a CMU channel is the following:

The architecture of the CMU offers 24-bit width registers for Global Clock Numerator, Denominator and individual clock divider counts with a maximum value of: 2²⁴ – 1.


Figure 2. Clock Management Unit(CMU)

After both CCM and CMU have been configured, the ATOM or the TOM configurations will be available.

The following configuration options are available for ATOM:

Clock source setting to any enabled CMU channel.
Working mode.
Trigger command.
Counting mode.
Signal polarity.
Update mode.
Period, duty cycle and timer counter ticks (offset/deadtime).

The GTM IP has 4 ATOM modules, each of them with 8 channels. The first configuration step is to select an ATOM module and enable one of the channels. The clock source of the channel can be set to any available CMU clock source.

Currently, only for SOMP working mode is supported in the PWM driver, the rest of the modes will be added in future work.

By setting the trigger command to Trigger OUT, an ATOM channel can be used internally to trigger the next channel in a cascading manner. If the trigger command is set to Reset on Trigger, the ATOM channel’s PWM signal is influenced by the signal of previous channels. In this way, the ATOM channels can be used to generate synchronized signals. An ATOM channel can be used to output its PWM signal by setting the channel output combo-box. Trigger command is currently not supported by the PWM driver and will be added.

The Counting Mode offers flexibility in setting the PWM generating mode: Centered-aligned (Up-Down counting) and Edge-aligned (Up counting).

The signal polarity of the ATOM channel can be set to HIGH/LOW. Together with the duty cycle and period options, the waveform of the ATOM channel can be easily configured.

The update mode is set by default to synchronous mode, as the PWM driver currently does not support async mode.

The period and duty cycle can be set via the available text boxes. The ratio between the period and the duty cycle should be a maximum of 1, otherwise a problem would occur. The counter offset is currently not supported driver-wise and will be added in future releases.

The architecture of the ATOM offers 24-bit width registers. For this reason, the maximum value for the period, duty cycle and counter ticks is equal to: 2²⁴ – 1.

More information about the ATOM configuration can be found in the in-tool documentation and use-cases, any of which represent a good starting point for development.


Figure 3. ATOM Channel Configuration

The following configuration options are available for TOM:

Clock source setting to the CMU fixed clock source.
Update mode.
Counting mode.
Signal Polarity.
Trigger Command.
Period, duty cycle and counter ticks.

The GTM IP has 2 TOM modules, each of them with 16 channels. The first configuration step is to select a TOM module and enable one of the channels. The clock source of the channel is set to the CMU fixed clock source. By design, the fixed clock source can be divided by 1, 16, 256, 4096 or 65536, offering some flexibility to the input clock frequency of the TOM channels. The architecture of the TOM offers 16-bit width registers. For this reason, the maximum value for the period, duty cycle and counter ticks is equal to: 2¹⁶ – 1.

The rest of the configuration options have the same limitations and yield the same behavior as the ATOM.


Figure 4. TOM Channel Configuration