From 76177aa280494bb36d7a0bcbda1078d4db717020 Mon Sep 17 00:00:00 2001 From: Ali Labbene Date: Mon, 9 Dec 2019 11:25:19 +0100 Subject: Official ARM version: v4.5 --- Documentation/Core/html/group__peripheral__gr.html | 351 +++++++++++++++++++++ 1 file changed, 351 insertions(+) create mode 100644 Documentation/Core/html/group__peripheral__gr.html (limited to 'Documentation/Core/html/group__peripheral__gr.html') diff --git a/Documentation/Core/html/group__peripheral__gr.html b/Documentation/Core/html/group__peripheral__gr.html new file mode 100644 index 0000000..fdd97e4 --- /dev/null +++ b/Documentation/Core/html/group__peripheral__gr.html @@ -0,0 +1,351 @@ + + + + + +Peripheral Access +CMSIS-CORE: Peripheral Access + + + + + + + + + + + + + + + +
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CMSIS-CORE +  Version 4.30 +
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CMSIS-CORE support for Cortex-M processor-based devices
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+Macros
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Peripheral Access
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Describes naming conventions, requirements, and optional features for accessing peripherals. +More...

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+Macros

#define _VAL2FLD(field, value)
 Mask and shift a bit field value for assigning to result to a peripheral register.
 
#define _FLD2VAL(field, value)
 Extract from a peripheral register value the a bit field value.
 
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Description

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The section below describes the naming conventions, requirements, and optional features for accessing device specific peripherals. Most of the rules also apply to the core peripherals. The Device Header File <device.h> contains typically these definition and also includes the core specific header files.

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Most of the definitions can be generated using the CMSIS-SVD System View Description for Peripherals. Refer to SVDConv.exe for more information.

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Each peripheral provides a data type definition with a name that is composed of:

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  • prefix <device abbreviation>_
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  • <peripheral name>
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  • postfix _Type or _TypeDef to identify a type definition.
    • +
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Example: LPC_UART_TypeDef for the device LPC and the peripheral UART.

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The data type definition uses standard C data types defined by the ANSI C header file <stdint.h>.

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  • IO Type Qualifiers are used to specify the access to peripheral variables. + + + + + + + + + + + + + + +
    IO Type Qualifier Type Description
    __IM Struct member Defines 'read only' permissions
    __OM Struct member Defines 'write only' permissions
    __IOM Struct member Defines 'read / write' permissions
    __I Scalar variable Defines 'read only' permissions
    __O Scalar variable Defines 'write only' permissions
    __IO Scalar variable Defines 'read / write' permissions
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    • +
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Note
__IM, __OM, __IOM are added in CMSIS-Core V4.20 to enhance support for C++. Prior version used __I, __O, __IO also for struct member definitions.
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The typedef <device abbreviation>_UART_TypeDef shown below defines the generic register layout for all UART channels in a device.

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typedef struct
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{
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union {
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__IM uint8_t RBR; /* Offset: 0x000 (R/ ) Receiver Buffer Register */
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__OM uint8_t THR; /* Offset: 0x000 ( /W) Transmit Holding Register */
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__IOM uint8_t DLL; /* Offset: 0x000 (R/W) Divisor Latch LSB */
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uint32_t RESERVED0;
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};
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union {
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__IOM uint8_t DLM; /* Offset: 0x004 (R/W) Divisor Latch MSB */
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__IOM uint32_t IER; /* Offset: 0x004 (R/W) Interrupt Enable Register */
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};
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union {
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__IM uint32_t IIR; /* Offset: 0x008 (R/ ) Interrupt ID Register */
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__OM uint8_t FCR; /* Offset: 0x008 ( /W) FIFO Control Register */
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};
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__IOM uint8_t LCR; /* Offset: 0x00C (R/W) Line Control Register */
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uint8_t RESERVED1[7];
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__IM uint8_t LSR; /* Offset: 0x014 (R/ ) Line Status Register */
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uint8_t RESERVED2[7];
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__IOM uint8_t SCR; /* Offset: 0x01C (R/W) Scratch Pad Register */
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uint8_t RESERVED3[3];
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__IOM uint32_t ACR; /* Offset: 0x020 (R/W) Autobaud Control Register */
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__IOM uint8_t ICR; /* Offset: 0x024 (R/W) IrDA Control Register */
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uint8_t RESERVED4[3];
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__IOM uint8_t FDR; /* Offset: 0x028 (R/W) Fractional Divider Register */
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uint8_t RESERVED5[7];
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__IOM uint8_t TER; /* Offset: 0x030 (R/W) Transmit Enable Register */
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uint8_t RESERVED6[39];
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__IM uint8_t FIFOLVL; /* Offset: 0x058 (R/ ) FIFO Level Register */
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} LPC_UART_TypeDef;
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To access the registers of the UART defined above, pointers to this register structure are defined. If more instances of a peripheral exist, the variables have a postfix (digit or letter) that identifies the peripheral.

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Example: In this example LPC_UART2 and LPC_UART3 are two pointers to UARTs defined with above register structure.
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#define LPC_UART2 ((LPC_UART_TypeDef *) LPC_UART2_BASE )
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#define LPC_UART3 ((LPC_UART_TypeDef *) LPC_UART3_BASE )
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The registers in the various UARTs can now be referred in the user code as shown below:
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val = LPC_UART2->DR // is the data register of UART1.
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+Minimal Requirements

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To access the peripheral registers and related function in a device, the files device.h and core_cm#.h define as a minimum:
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  • The Register Layout Typedef for each peripheral that defines all register names. RESERVED is used to introduce space into the structure for adjusting the addresses of the peripheral registers.
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    + Example:
    typedef struct
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    {
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    __IOM uint32_t CTRL; /* Offset: 0x000 (R/W) SysTick Control and Status Register */
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    __IOM uint32_t LOAD; /* Offset: 0x004 (R/W) SysTick Reload Value Register */
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    __IOM uint32_t VAL; /* Offset: 0x008 (R/W) SysTick Current Value Register */
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    __IM uint32_t CALIB; /* Offset: 0x00C (R/ ) SysTick Calibration Register */
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    } SysTick_Type;
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    • +
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  • Base Address for each peripheral (in case of multiple peripherals that use the same register layout typedef multiple base addresses are defined).
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    + Example:
    #define SysTick_BASE (SCS_BASE + 0x0010) /* SysTick Base Address */
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    • +
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  • Access Definitions for each peripheral. In case of multiple peripherals that are using the same register layout typdef, multiple access definitions exist (LPC_UART0, LPC_UART2).
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    + Example:
    #define SysTick ((SysTick_Type *) Systick_BASE) /* SysTick access definition */
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    • +
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These definitions allow accessing peripheral registers with simple assignments.

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  • Example:
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    SysTick->CTRL = 0;
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    • +
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+Optional Features

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Optionally, the file device.h may define:

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  • Register Bit Fields and #define constants that simplify access to peripheral registers. These constants may define bit-positions or other specific patterns that are required for programming peripheral registers. The identifiers should start with <device abbreviation>_ and <peripheral name>_. It is recommended to use CAPITAL letters for #define constants.
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  • More complex functions (i.e. status query before a sending register is accessed). Again, these functions start with <device abbreviation>_ and <peripheral name>_.
    • +
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+Register Bit Fields

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For Core Register, macros define the position and the mask value for a bit field. It is recommended to create such definitions also for other peripheral registers.

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Example:

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Bit field definitions for register CPUID in SCB (System Control Block).

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/* SCB CPUID Register Definitions */
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#define SCB_CPUID_IMPLEMENTER_Pos 24U
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#define SCB_CPUID_IMPLEMENTER_Msk (0xFFUL << SCB_CPUID_IMPLEMENTER_Pos)
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#define SCB_CPUID_VARIANT_Pos 20U
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#define SCB_CPUID_VARIANT_Msk (0xFUL << SCB_CPUID_VARIANT_Pos)
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#define SCB_CPUID_ARCHITECTURE_Pos 16U
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#define SCB_CPUID_ARCHITECTURE_Msk (0xFUL << SCB_CPUID_ARCHITECTURE_Pos)
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#define SCB_CPUID_PARTNO_Pos 4U
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#define SCB_CPUID_PARTNO_Msk (0xFFFUL << SCB_CPUID_PARTNO_Pos)
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#define SCB_CPUID_REVISION_Pos 0U
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#define SCB_CPUID_REVISION_Msk (0xFUL /*<< SCB_CPUID_REVISION_Pos*/)
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The macros _VAL2FLD(field, value) and _FLD2VAL(field, value) enable access to bit fields.

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Macro Definition Documentation

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#define _FLD2VAL( field,
 value 
)
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Parameters
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fieldname of bit field.
valuevalue of the register
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The macro _FLD2VAL uses the #define's _Pos and _Msk of the related bit field to extract the value of a bit field from a register.

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Example:

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id = = _FLD2VAL(SCB_CPUID_REVISION, SCB->CPUID);
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#define _VAL2FLD( field,
 value 
)
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Parameters
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fieldname of bit field.
valuevalue for the bit field.
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The macro _VAL2FLD uses the #define's _Pos and _Msk of the related bit field to shift bit-field values for assigning to a register.

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Example:

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SCB->CPUID = _VAL2FLD(SCB_CPUID_REVISION, 0x3) | _VAL2FLD(SCB_CPUID_VARIANT, 0x3);
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+ + + + -- cgit