internal-flag fields behave like flag fields, but instead of the flags being set by an external signal, it is set by an internal signal. This may for instance be used in conjunction with the overrun output of an MMIO to stream field.

This structure supports the following configuration keys.

Configure the existence and behavior of the hardware read port.

The following values are supported:

• disabled (default): no read port is generated.

• simple: only the data output is generated.

This key is optional unless required by context. If not specified, the default value (disabled) is used.

Configures the reset value.

The following values are supported:

• no (default): the internal data register resets to 0, with the valid flag set.

• yes: the internal data register resets to 1, with the valid flag set.

• an integer: the internal data register resets to the given value, with the valid flag set.

• generic: the reset value is controlled through a VHDL generic.

This key is optional unless required by context. If not specified, the default value (no) is used.

Configures strobing an internal signal when a bit-set operation to a bit that was already set occurs. This essentially serves as an overflow signal for flag fields.

The following values are supported:

• null (default): the feature is disabled.

• a string matching [a-zA-Z][a-zA-Z0-9_]*: an internal signal with the given name is created (if necessary) and strobed when a bit-set operation occurs to an already-set bit.

This key is optional unless required by context. If not specified, the default value (null) is used.

Configures strobing an internal signal when a bit-clear operation to a bit that was already cleared occurs. This essentially serves as an underflow signal for flag fields.

The following values are supported:

• null (default): the feature is disabled.

• a string matching [a-zA-Z][a-zA-Z0-9_]*: an internal signal with the given name is created (if necessary) and strobed when a bit-clear operation occurs to an already-cleared bit.

This key is optional unless required by context. If not specified, the default value (null) is used.

Configures the internal signal that is to be monitored. The value must be a string matching [a-zA-Z][a-zA-Z0-9_]*.

This key is required.