Note: This needs to be rewritten.

Defined symbols

HWA defines the following symbols describing the target device and its hardware configuration:

Symbol	Comments
`HW_DEVICE`	The device name as passed to the compiler
`HW_DEVICE_ATMEGAXU4`	Defined void
`HW_DEVICE_ATMEGA32U4_MU`	Defined void depending on the HWA header included
`HW_DEVICE_PACKAGE_44Q`	Defined void
`HW_DEVICE_RAM_START`	Address of first RAM byte (after registers and I/O regs)
`HW_DEVICE_APP_START`	Address of first application byte (after IRQ vector table)

Symbol	ATmega16U4	ATmega32U4
`HW_DEVICE`		atmega32u4
`HW_DEVICE_SIGNATURE`		0x1E,0x95,0x87
`HW_DEVICE_FLASH_SIZE`		32768
`HW_DEVICE_FLASH_PAGE_SIZE`		128
`HW_DEVICE_EEPROM_SIZE`		1024
`HW_DEVICE_EEPROM_PAGE_SIZE`		4
`HW_DEVICE_RAM_SIZE`		2560
`HW_DEVICE_RAM_START`		0x0100
`HW_DEVICE_APP_START`		0x00AC

Configuration fuses

ATmegaXU4 devices hold 3 fuse bytes describing their hardware configuration. HWA computes the value of these fuse bytes from the fuse values (detailed in the following subsections) that must be defined prior to including the HWA header. Factory defaults (shown with a bold face) are used for values that are undefined as the HWA header is included.

Symbol	Comments
`HW_DEVICE_FUSE_EB`	Fuse extended byte
`HW_DEVICE_FUSE_HB`	Fuse high byte
`HW_DEVICE_FUSE_LB`	Fuse low byte

Clocking

HWA uses these settings to compute the system clock frequency syshz.

Symbol	Valid values	Comments
`HW_DEVICE_CLK_SRC`	`external` `rc_8MHz` `low_freq_xosc` `low_power_xosc`	External source on pin CLKI Internal RC calibrated oscillator Crystal/resonator oscillator between pins XTAL1 and XTAL2
`HW_DEVICE_CLK_SRC_HZ`	Positive integer	Clock frequency for `external` and `xosc` clock source
`HW_DEVICE_CLK_PSC`	`8` `1`	Clock divided by 8 Clock not divided

Startup delays

Symbol	Valid values	Comments
`HW_DEVICE_STARTUP_DELAYS`	`4CK` `4CK_4ms` `4CK_64ms` `6CK_14CK` `6CK_14CK_4ms` `6CK_14CK_64ms` `1KCK_4ms` `1KCK_64ms` `32KCK_64ms` `258CK_14CK_4ms` `258CK_14CK_64ms` `1KCK_14CK` `1KCK_14CK_4ms` `1KCK_14CK_64ms` `16KCK_14CK` `16KCK_14CK_4ms` `16KCK_14CK_64ms`	Valid values depend on the clocking configuration

Other fuses

Symbol	Valid values	Comments
`HW_DEVICE_PIN_HWB`	`enabled` `disabled`	Whether the HWB pin allows to execute the bootloader section after reset when tied to ground during external reset pulse.
`HW_DEVICE_BROWNOUT_DETECTION`	`off` `1800_2200mV` `2000_2400mV` `2200_2600mV` `2400_2800mV` `3200_3600mV` `3300_3700mV` `4000_4500mV`	Brown-out detection level
`HW_DEVICE_ON_CHIP_DEBUG`	`enabled` `disabled`	Whether on-chip debugging is enabled
`HW_DEVICE_JTAG`	`enabled` `disabled`	Whether the JTAG interface is enabled
`HW_DEVICE_SERIAL_PROGRAMMING`	`enabled` `disabled`	Whether the device can be programmed via the SPI
`HW_DEVICE_WATCHDOG_ALWAYS_ON`	`yes` `no`	Whether the watchdog is always running
`HW_DEVICE_PRESERVE_EEPROM_THROUGH_CHIP_ERASE`	`enabled` `disabled`	Whether the EEPROM memory is erased when a chip erase occurs
`HW_DEVICE_BOOT`	`application` `bootloader`	Whether the device starts the application or the bootloader after reset
`HW_DEVICE_BOOTSECTION_SIZE`	`512` `1024` `2048` `4096`	Size of the boot section
`HW_DEVICE_CLOCK_OUTPUT`	`enabled` `disabled`	Whether the device outputs its clock

Peripherals

Note A missing class name means that the peripheral is not implemented yet.

Object name	Class	Comments
`core0`	_corec	The core
`watchdog0`	_wdb	Watchdog (WDG)
`portb`	_gpa	General purpose I/O port B (PORTB)
`portc`	_gpa	General purpose I/O port C (PORTC)
`portd`	_gpa	General purpose I/O port D (PORTD)
`porte`	_gpa	General purpose I/O port D (PORTE)
`portf`	_gpa	General purpose I/O port D (PORTF)
`int0`	_inta	External interrupt INT0
`int1`	_inta	External interrupt INT1
`int2`	_inta	External interrupt INT2
`int3`	_inta	External interrupt INT3
`int6`	_inta	External interrupt INT6
`pcic0`	_pxa	Pin change interrupt controller
`prescaler0`	_psa	counter0/1/3 prescaler (PSC0)
`counter0`	_cta	8-bit counter-timer (T0)
`counter0compare0`	_oca	Compare unit 0 of counter0 (OC0A)
`counter0compare1`	_oca	Compare unit 1 of counter0 (OC0B)
`counter1`	_cte	16-bit counter-timer (T1)
`counter1compare0`	_occ	Compare unit 0 of counter1 (OC1A)
`counter1compare1`	_occ	Compare unit 1 of counter1 (OC1B)
`counter1compare2`	_occ	Compare unit 2 of counter1 (OC1C)
`counter1capture0`	_ica	Capture unit of counter1 (ICP1)
`counter3`	_cte	16-bit counter-timer (T1)
`counter3compare0`	_occ	Compare unit 0 of counter3 (OC3A)
`counter3compare1`	_occ	Compare unit 1 of counter3 (OC3B)
`counter3compare2`	_occ	Compare unit 2 of counter3 (OC3C)
`counter3capture0`	_ica	Capture unit of counter3 (ICP3)
`acmp0`	_aca	Analog Comparator
`eeprom0`	_eea	Eeprom memory
`flash0`	_fla	Flash memory

Interrupts

Interrupt definition	Atmel label	Comments
`watchdog0`	WDT	Watchdog Time-out Interrupt
`eeprom0`	EE READY	EEPROM ready
`eeprom0,ready`	EE READY	EEPROM ready
`flash0`	SPM READY	Store Program Memory Ready

I/O ports and pins

HWA name	44Q	Class	Atmel name
`port_b`		_ioa	PORTB
`(portb,0)`	`pin_8`	_ioa	PB0
`(portb,1)`	`pin_9`	_ioa	PB1
`(portb,2)`	`pin_10`	_ioa	PB2
`(portb,3)`	`pin_11`	_ioa	PB3
`(portb,4)`	`pin_28`	_ioa	PB4
`(portb,5)`	`pin_29`	_ioa	PB5
`(portb,6)`	`pin_30`	_ioa	PB6
`(portb,7)`	`pin_12`	_ioa	PB7
`port_c`		_ioa	PORTC
`(portc,6)`	`pin_31`	_ioa	PC6
`(portc,7)`	`pin_32`	_ioa	PC7
`port_d`		_ioa	PORTD
`(portd,0)`	`pin_18`	_ioa	PD0
`(portd,1)`	`pin_19`	_ioa	PD1
`(portd,2)`	`pin_20`	_ioa	PD2
`(portd,3)`	`pin_21`	_ioa	PD3
`(portd,4)`	`pin_25`	_ioa	PD4
`(portd,5)`	`pin_22`	_ioa	PD5
`(portd,6)`	`pin_26`	_ioa	PD6
`(portd,7)`	`pin_27`	_ioa	PD7
`port_e`		_ioa	PORTE
`pe2`	`pin_33`	_ioa	PE2
`pe6`	`pin_1`	_ioa	PE6
`port_f`		_ioa	PORTF
`pf0`	`pin_41`	_ioa	PF0
`pf1`	`pin_40`	_ioa	PF1
`pf4`	`pin_39`	_ioa	PF4
`pf5`	`pin_38`	_ioa	PF5
`pf6`	`pin_37`	_ioa	PF6
`pf7`	`pin_36`	_ioa	PF7