Overview

The MCUXpresso SDK provides a peripheral driver for the Crossbar External Bus Interface (FlexBus) block of MCUXpresso SDK devices.

A multifunction external bus interface is provided on the device with a basic functionality to interface to slave-only devices. It can be directly connected to the following asynchronous or synchronous devices with little or no additional circuitry.

External ROMs
Flash memories
Programmable logic devices
Other simple target (slave) devices

For asynchronous devices, a simple chip-select based interface can be used. The FlexBus interface has up to six general purpose chip-selects, FB_CS[5:0]. The number of chip selects available depends on the device and its pin configuration.

FlexBus functional operation

To configure the FlexBus driver, use on of the two ways to configure the flexbus_config_t structure.

Using the FLEXBUS_GetDefaultConfig() function.
Set parameters in the flexbus_config_t structure.

To initialize and configure the FlexBus driver, call the FLEXBUS_Init() function and pass a pointer to the flexbus_config_t structure.

To de-initialize the FlexBus driver, call the FLEXBUS_Deinit() function.

Typical use case and example

This example shows how to write/read to external memory (MRAM) by using the FlexBus module.

flexbus_config_t flexbusUserConfig;
FLEXBUS_GetDefaultConfig(&flexbusUserConfig); /* Gets the default configuration. */
/* Configure some parameters when using MRAM */
flexbusUserConfig.waitStates            = 2U;                 /* Wait 2 states */
flexbusUserConfig.chipBaseAddress       = MRAM_START_ADDRESS; /* MRAM address for using FlexBus */
flexbusUserConfig.chipBaseAddressMask   = 7U;                 /* 512 kilobytes memory size */
FLEXBUS_Init(FB, &flexbusUserConfig); /* Initializes and configures the FlexBus module */
/* Do something */
FLEXBUS_Deinit(FB);

Data Structures
struct	flexbus_config_t
	Configuration structure that the user needs to set. More...

Enumerations
enum	flexbus_port_size_t { kFLEXBUS_4Bytes = 0x00U, kFLEXBUS_1Byte = 0x01U, kFLEXBUS_2Bytes = 0x02U }
	Defines port size for FlexBus peripheral. More...

enum	flexbus_write_address_hold_t { kFLEXBUS_Hold1Cycle = 0x00U, kFLEXBUS_Hold2Cycles = 0x01U, kFLEXBUS_Hold3Cycles = 0x02U, kFLEXBUS_Hold4Cycles = 0x03U }
	Defines number of cycles to hold address and attributes for FlexBus peripheral. More...

enum	flexbus_read_address_hold_t { kFLEXBUS_Hold1Or0Cycles = 0x00U, kFLEXBUS_Hold2Or1Cycles = 0x01U, kFLEXBUS_Hold3Or2Cycle = 0x02U, kFLEXBUS_Hold4Or3Cycle = 0x03U }
	Defines number of cycles to hold address and attributes for FlexBus peripheral. More...

enum	flexbus_address_setup_t { kFLEXBUS_FirstRisingEdge = 0x00U, kFLEXBUS_SecondRisingEdge = 0x01U, kFLEXBUS_ThirdRisingEdge = 0x02U, kFLEXBUS_FourthRisingEdge = 0x03U }
	Address setup for FlexBus peripheral. More...

enum	flexbus_bytelane_shift_t { kFLEXBUS_NotShifted = 0x00U, kFLEXBUS_Shifted = 0x01U }
	Defines byte-lane shift for FlexBus peripheral. More...

enum	flexbus_multiplex_group1_t { kFLEXBUS_MultiplexGroup1_FB_ALE = 0x00U, kFLEXBUS_MultiplexGroup1_FB_CS1 = 0x01U, kFLEXBUS_MultiplexGroup1_FB_TS = 0x02U }
	Defines multiplex group1 valid signals. More...

enum	flexbus_multiplex_group2_t { kFLEXBUS_MultiplexGroup2_FB_CS4 = 0x00U, kFLEXBUS_MultiplexGroup2_FB_TSIZ0 = 0x01U, kFLEXBUS_MultiplexGroup2_FB_BE_31_24 = 0x02U }
	Defines multiplex group2 valid signals. More...

enum	flexbus_multiplex_group3_t { kFLEXBUS_MultiplexGroup3_FB_CS5 = 0x00U, kFLEXBUS_MultiplexGroup3_FB_TSIZ1 = 0x01U, kFLEXBUS_MultiplexGroup3_FB_BE_23_16 = 0x02U }
	Defines multiplex group3 valid signals. More...

enum	flexbus_multiplex_group4_t { kFLEXBUS_MultiplexGroup4_FB_TBST = 0x00U, kFLEXBUS_MultiplexGroup4_FB_CS2 = 0x01U, kFLEXBUS_MultiplexGroup4_FB_BE_15_8 = 0x02U }
	Defines multiplex group4 valid signals. More...

enum	flexbus_multiplex_group5_t { kFLEXBUS_MultiplexGroup5_FB_TA = 0x00U, kFLEXBUS_MultiplexGroup5_FB_CS3 = 0x01U, kFLEXBUS_MultiplexGroup5_FB_BE_7_0 = 0x02U }
	Defines multiplex group5 valid signals. More...

Driver version
#define	FSL_FLEXBUS_DRIVER_VERSION (MAKE_VERSION(2, 0, 1))
	Version 2.0.1. More...

FlexBus functional operation
void	FLEXBUS_Init (FB_Type base, const flexbus_config_t config)
	Initializes and configures the FlexBus module. More...

void	FLEXBUS_Deinit (FB_Type *base)
	De-initializes a FlexBus instance. More...

void	FLEXBUS_GetDefaultConfig (flexbus_config_t *config)
	Initializes the FlexBus configuration structure. More...

Data Structure Documentation

struct flexbus_config_t

Data Fields
uint8_t	chip
	Chip FlexBus for validation.

uint8_t	waitStates
	Value of wait states.

uint32_t	chipBaseAddress
	Chip base address for using FlexBus.

uint32_t	chipBaseAddressMask
	Chip base address mask.

bool	writeProtect
	Write protected.

bool	burstWrite
	Burst-Write enable.

bool	burstRead
	Burst-Read enable.

bool	byteEnableMode
	Byte-enable mode support.

bool	autoAcknowledge
	Auto acknowledge setting.

bool	extendTransferAddress
	Extend transfer start/extend address latch enable.

bool	secondaryWaitStates
	Secondary wait states number.

flexbus_port_size_t	portSize
	Port size of transfer.

flexbus_bytelane_shift_t	byteLaneShift
	Byte-lane shift enable.

flexbus_write_address_hold_t	writeAddressHold
	Write address hold or deselect option.

flexbus_read_address_hold_t	readAddressHold
	Read address hold or deselect option.

flexbus_address_setup_t	addressSetup
	Address setup setting.

flexbus_multiplex_group1_t	group1MultiplexControl
	FlexBus Signal Group 1 Multiplex control.

flexbus_multiplex_group2_t	group2MultiplexControl
	FlexBus Signal Group 2 Multiplex control.

flexbus_multiplex_group3_t	group3MultiplexControl
	FlexBus Signal Group 3 Multiplex control.

flexbus_multiplex_group4_t	group4MultiplexControl
	FlexBus Signal Group 4 Multiplex control.

flexbus_multiplex_group5_t	group5MultiplexControl
	FlexBus Signal Group 5 Multiplex control.

Macro Definition Documentation

#define FSL_FLEXBUS_DRIVER_VERSION (MAKE_VERSION(2, 0, 1))

Enumeration Type Documentation

enum flexbus_port_size_t

Enumerator
kFLEXBUS_4Bytes	32-bit port size
kFLEXBUS_1Byte	8-bit port size
kFLEXBUS_2Bytes	16-bit port size

enum flexbus_write_address_hold_t

Enumerator
kFLEXBUS_Hold1Cycle	Hold address and attributes one cycles after FB_CSn negates on writes.
kFLEXBUS_Hold2Cycles	Hold address and attributes two cycles after FB_CSn negates on writes.
kFLEXBUS_Hold3Cycles	Hold address and attributes three cycles after FB_CSn negates on writes.
kFLEXBUS_Hold4Cycles	Hold address and attributes four cycles after FB_CSn negates on writes.

enum flexbus_read_address_hold_t

Enumerator
kFLEXBUS_Hold1Or0Cycles	Hold address and attributes 1 or 0 cycles on reads.
kFLEXBUS_Hold2Or1Cycles	Hold address and attributes 2 or 1 cycles on reads.
kFLEXBUS_Hold3Or2Cycle	Hold address and attributes 3 or 2 cycles on reads.
kFLEXBUS_Hold4Or3Cycle	Hold address and attributes 4 or 3 cycles on reads.

enum flexbus_address_setup_t

Enumerator
kFLEXBUS_FirstRisingEdge	Assert FB_CSn on first rising clock edge after address is asserted.
kFLEXBUS_SecondRisingEdge	Assert FB_CSn on second rising clock edge after address is asserted.
kFLEXBUS_ThirdRisingEdge	Assert FB_CSn on third rising clock edge after address is asserted.
kFLEXBUS_FourthRisingEdge	Assert FB_CSn on fourth rising clock edge after address is asserted.

enum flexbus_bytelane_shift_t

Enumerator

kFLEXBUS_NotShifted

Not shifted.

Data is left-justified on FB_AD

kFLEXBUS_Shifted

Shifted.

Data is right justified on FB_AD

enum flexbus_multiplex_group1_t

Enumerator
kFLEXBUS_MultiplexGroup1_FB_ALE	FB_ALE.
kFLEXBUS_MultiplexGroup1_FB_CS1	FB_CS1.
kFLEXBUS_MultiplexGroup1_FB_TS	FB_TS.

enum flexbus_multiplex_group2_t

Enumerator
kFLEXBUS_MultiplexGroup2_FB_CS4	FB_CS4.
kFLEXBUS_MultiplexGroup2_FB_TSIZ0	FB_TSIZ0.
kFLEXBUS_MultiplexGroup2_FB_BE_31_24	FB_BE_31_24.

enum flexbus_multiplex_group3_t

Enumerator
kFLEXBUS_MultiplexGroup3_FB_CS5	FB_CS5.
kFLEXBUS_MultiplexGroup3_FB_TSIZ1	FB_TSIZ1.
kFLEXBUS_MultiplexGroup3_FB_BE_23_16	FB_BE_23_16.

enum flexbus_multiplex_group4_t

Enumerator
kFLEXBUS_MultiplexGroup4_FB_TBST	FB_TBST.
kFLEXBUS_MultiplexGroup4_FB_CS2	FB_CS2.
kFLEXBUS_MultiplexGroup4_FB_BE_15_8	FB_BE_15_8.

enum flexbus_multiplex_group5_t

Enumerator
kFLEXBUS_MultiplexGroup5_FB_TA	FB_TA.
kFLEXBUS_MultiplexGroup5_FB_CS3	FB_CS3.
kFLEXBUS_MultiplexGroup5_FB_BE_7_0	FB_BE_7_0.

Function Documentation

void FLEXBUS_Init	(	FB_Type *	base,
		const flexbus_config_t *	config
	)

This function enables the clock gate for FlexBus module. Only chip 0 is validated and set to known values. Other chips are disabled. Note that in this function, certain parameters, depending on external memories, must be set before using the FLEXBUS_Init() function. This example shows how to set up the uart_state_t and the flexbus_config_t parameters and how to call the FLEXBUS_Init function by passing in these parameters.

flexbus_config_t flexbusConfig;
FLEXBUS_GetDefaultConfig(&flexbusConfig);
flexbusConfig.waitStates            = 2U;
flexbusConfig.chipBaseAddress       = 0x60000000U;
flexbusConfig.chipBaseAddressMask   = 7U;
FLEXBUS_Init(FB, &flexbusConfig);

Parameters

base	FlexBus peripheral address.
config	Pointer to the configuration structure

void FLEXBUS_Deinit ( FB_Type * base )

This function disables the clock gate of the FlexBus module clock.

Parameters

base	FlexBus peripheral address.

void FLEXBUS_GetDefaultConfig ( flexbus_config_t * config )

This function initializes the FlexBus configuration structure to default value. The default values are.

fbConfig->chip                   = 0;
fbConfig->writeProtect           = 0;
fbConfig->burstWrite             = 0;
fbConfig->burstRead              = 0;
fbConfig->byteEnableMode         = 0;
fbConfig->autoAcknowledge        = true;
fbConfig->extendTransferAddress  = 0;
fbConfig->secondaryWaitStates    = 0;
fbConfig->byteLaneShift          = kFLEXBUS_NotShifted;
fbConfig->writeAddressHold       = kFLEXBUS_Hold1Cycle;
fbConfig->readAddressHold        = kFLEXBUS_Hold1Or0Cycles;
fbConfig->addressSetup           = kFLEXBUS_FirstRisingEdge;
fbConfig->portSize               = kFLEXBUS_1Byte;
fbConfig->group1MultiplexControl = kFLEXBUS_MultiplexGroup1_FB_ALE;
fbConfig->group2MultiplexControl = kFLEXBUS_MultiplexGroup2_FB_CS4 ;
fbConfig->group3MultiplexControl = kFLEXBUS_MultiplexGroup3_FB_CS5;
fbConfig->group4MultiplexControl = kFLEXBUS_MultiplexGroup4_FB_TBST;
fbConfig->group5MultiplexControl = kFLEXBUS_MultiplexGroup5_FB_TA;

Parameters

config Pointer to the initialization structure.

See Also: FLEXBUS_Init

Overview

FlexBus functional operation

Typical use case and example

Data Structures

Enumerations

Driver version