FieldNode

FieldNode is a template class that represents a field component in SystemRDL.
FieldNode is the lowest node in the hierarchy, and it can only be instantiated within a RegNode component.

FieldBase

FieldBase is a base class providing constexpr constants for basic information about the field. The base class does not provide any write or read capabilities.

It is a template that takes the following template arguments

template <uint32_t START_BIT, uint32_t END_BIT, typename PARENT_TYPE>
class FieldBase;

START_BIT and END_BIT represent the position of the field within the containing register. They are integers and represent LSB and MSB respectively.

PARENT_TYPE accepts a specialization of a RegNode template, and is the type of the containing register. It is necessary to pass this type, because the write and read methods of the field will pass these requests to the parent register, along with the value written.

FieldRdMixin and FieldWrMixin

Since the FieldBase class does not provide any write or read capabilities, these two Mixins are supposed to provide the additional capabilities to the fields. They are supposed to provide setters and getters for the fields, along with operator overloads. The memory access is not done by these mixins, but the requests are instead passed to the register nodes.

Field access methods

The 2 mixins will provide at least the get() and set() methods for accessing the field. The execution of getters and setters will depend on the type of the containing register.

Writing to a field

In case of a writing a value to a field there are 2 cases.

1. Containing register is write only

In this case the value passed to the register for writing will just be the value written to the field shifted by LSB. This will correspond to only 1 write memory access, and an additional shifting operation if the passed value is a variable.

2. Containing register is rw

In this case it is necessary to read first the register value and apply a mask corresponding to the location of the field.

The field set() method will first read a value from the containing register, apply a mask, and | (OR) the value with the shifted value of the passed argument to the set() method.

This will correspond to 1 read memory operation first, followed by arithmetic operations for masking (can vary) and a write memory operation.

Reading from a field

In case of reading from a field, the operation does not depend on the containing register, and the value returned from get() function will just be containing register value with applied mask and shifted right by LSB. It will in this case have 1 read memory access, and arithmetic operation for mask and shifting (can vary).

FieldNode

FieldNode is a template class inheriting the parameter pack of mixins. The prototype is as shown:

template <typename... FieldMixins>
class FieldNode : public FieldMixins...

In order to provide Registers and Fields that have Read, Write or ReadWrite capabilities, the templates FieldNode are inheriting parameter pack of Mixins meant to provide the additional functionality.

For example:

• FieldNode inheriting only FieldRdMixin will be a read-only field.
• FieldNode inheriting only FieldWrMixin will be a write-only field.
• FieldNode inheriting both FieldWrMixin and FieldRdMixin will be a read-write field.

In order to ease the use of these templates, common specializations of FieldNode is already provided under the names:

FieldRO

is a read-only field with a declaration:

template <uint32_t START_BIT, uint32_t END_BIT, typename PARENT_TYPE>
using FieldRO = ...

FieldWO

is a write-only field with a declaration:

template <uint32_t START_BIT, uint32_t END_BIT, typename PARENT_TYPE>
using FieldWO = ...

FieldRW

is a read-write field with a declaration:

template <uint32_t START_BIT, uint32_t END_BIT, typename PARENT_TYPE>
using FieldRW = ...

It is advised to use these specializations to construct your fields.