Extensions to the Register Section

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Extensions to the Register Section
SVD Extension in Version 1.1

The following elements have been added to the register section. All new elements are optional.

Element Name | Description | Type | Occurrence
--- | --- | --- | ---
alternateRegister | This tag can reference a register that has been defined above to current location in the description and that describes the memory location already. This tells the SVDConv's address checker that the redefinition of this particular register is intentional. The register name needs to be unique within the scope of the current peripheral. A register description is defined either for a unique address location or could be a redefinition of an already described address. In the latter case, the register can be either marked alternateRegister and needs to have a unique name, or it can have the same register name but is assigned to a register subgroup through the tag alternateGroup (specified in version 1.0). | identifierType | 0..1

dataType

It can be useful to assign a specific native C datatype to a register. This helps avoiding type casts. For example, if a 32 bit register shall act as a pointer to a 32 bit unsigned data item, then dataType can be set to "uint32_t *". The following simple data types are predefined:

- uint8_t: unsigned byte
- uint16_t: unsigned half word
- uint32_t: unsigned word
- uint64_t: unsigned double word
- int8_t: signed byte
- int16_t: signed half word
- int32_t: signed world
- int64_t: signed double word
- uint8_t *: pointer to unsigned byte
- uint16_t *: pointer to unsigned half word
- uint32_t *: pointer to unsigned word
- uint64_t *: pointer to unsigned double word
- int8_t *: pointer to signed byte
- int16_t *: pointer to signed half word
- int32_t *: pointer to signed world
- int64_t *: pointer to signed double word

dataTypeType

0..1

## Example:

    ...
    <register>
        <name>TIM_MODEA</name>
        <description>In mode A this register acts as a reload value</description>
        <addressOffset>0xC</addressOffset>
    </register>
    <register>
        <name>TIM_MODEB</name>
        <description>In mode B this register acts as the compare value</description>
        <alternateRegister>TIM_MODEA</alternateRegister>
        <addressOffset>0xC</addressOffset>
    </register>
    <register>
        <name>DMA_DATA</name>
        <description>This register contains the address of the data being transferred</description>
        <dataType>uint32_t *</dataType>
        <addressOffset>0xf0</addressOffset>
    </register>
    ...

This example describes two registers, TIM_MODEA and TIM_MODEB. Both have the same address offset. Based on the configured operation model being A or B, the register acts as reload or compare value. The register DMA_DATA is specified as a pointer to unsigned word data. The code generated for the device header file is:

    typedef struct {
      union {
        __IO   uint32_t TIM_MODEA;
        __IO   uint32_t TIM_MODEB;
            };
      __IO uint32_t * DMA_DATA;
      ...
    } <peripheral:name>_Type;