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//! # Two-wire Automotive Interface (TWAI)
//!
//! ## Overview
//! The TWAI peripheral driver provides functions and structs specifically
//! designed for the Two-Wire Automotive Interface (TWAI) on ESP chips. TWAI is
//! a communication protocol commonly used in automotive applications for
//! sending and receiving messages between electronic control units (ECUs) in a
//! vehicle.
//!
//! The driver enables you to configure and utilize the TWAI module on ESP
//! chips. It offers functions for initializing the TWAI peripheral, setting up
//! the timing parameters, configuring acceptance filters, handling interrupts,
//! and transmitting/receiving messages on the TWAI bus.
//!
//! This driver manages the ISO 11898-1 (CAN Specification 2.0) compatible TWAI
//! controllers. It supports Standard Frame Format (11-bit) and Extended Frame
//! Format (29-bit) frame identifiers.
//!
//! ## Example
//! ```no_run
//! // Use GPIO pins 2 and 3 to connect to the respective pins on the CAN
//! // transceiver.
//! let can_tx_pin = io.pins.gpio2;
//! let can_rx_pin = io.pins.gpio3;
//!
//! // The speed of the CAN bus.
//! const CAN_BAUDRATE: twai::BaudRate = twai::BaudRate::B1000K;
//!
//! // Begin configuring the TWAI peripheral. The peripheral is in a reset like
//! // state that prevents transmission but allows configuration.
//! let mut can_config = twai::TwaiConfiguration::new(
//! peripherals.TWAI0,
//! can_tx_pin,
//! can_rx_pin,
//! &clocks,
//! CAN_BAUDRATE,
//! );
//!
//! // Partially filter the incoming messages to reduce overhead of receiving undesired messages
//! const FILTER: twai::filter::SingleStandardFilter =
//! twai::filter::SingleStandardFilter::new(b"xxxxxxxxxx0", b"x", [b"xxxxxxxx", b"xxxxxxxx"]);
//! can_config.set_filter(FILTER);
//!
//! // Start the peripheral. This locks the configuration settings of the peripheral
//! // and puts it into operation mode, allowing packets to be sent and
//! // received.
//! let mut can = can_config.start();
//!
//! loop {
//! // Wait for a frame to be received.
//! let frame = block!(can.receive()).unwrap();
//!
//! println!("Received a frame:");
//!
//! // Print different messages based on the frame id type.
//! match frame.id() {
//! Id::Standard(id) => {
//! println!("\tStandard Id: {:?}", id);
//! }
//! Id::Extended(id) => {
//! println!("\tExtended Id: {:?}", id);
//! }
//! }
//!
//! // Print out the frame data or the requested data length code for a remote
//! // transmission request frame.
//! if frame.is_data_frame() {
//! println!("\tData: {:?}", frame.data());
//! } else {
//! println!("\tRemote Frame. Data Length Code: {}", frame.dlc());
//! }
//!
//! // Transmit the frame back.
//! let _result = block!(can.transmit(&frame)).unwrap();
//! }
//! ```
#[cfg(feature = "eh1")]
use embedded_can::{nb::Can, Error, ErrorKind, ExtendedId, Frame, Id, StandardId};
#[cfg(not(feature = "eh1"))]
use embedded_hal::can::{Can, Error, ErrorKind, ExtendedId, Frame, Id, StandardId};
use fugit::HertzU32;
use self::filter::{Filter, FilterType};
use crate::{
clock::Clocks,
gpio::{InputPin, InputSignal, OutputPin, OutputSignal},
peripheral::{Peripheral, PeripheralRef},
peripherals::twai0::RegisterBlock,
system::{self, PeripheralClockControl},
};
pub mod filter;
/// Structure backing the embedded_hal::can::Frame/embedded_can::Frame trait.
#[derive(Clone, Copy, Debug)]
pub struct EspTwaiFrame {
id: Id,
dlc: usize,
data: [u8; 8],
is_remote: bool,
}
impl EspTwaiFrame {
/// Make a new frame from an id, pointer to the TWAI_DATA_x_REG registers,
/// and the length of the data payload (dlc).
///
/// # Safety
/// This is unsafe because it directly accesses peripheral registers.
unsafe fn new_from_data_registers(
id: impl Into<Id>,
registers: *const u32,
dlc: usize,
) -> Self {
let mut data: [u8; 8] = [0; 8];
// Copy the data from the memory mapped peripheral into actual memory.
copy_from_data_register(&mut data[..dlc], registers);
Self {
id: id.into(),
data,
dlc,
is_remote: false,
}
}
}
impl Frame for EspTwaiFrame {
fn new(id: impl Into<Id>, data: &[u8]) -> Option<Self> {
// CAN2.0 frames cannot contain more than 8 bytes of data.
if data.len() > 8 {
return None;
}
let mut d: [u8; 8] = [0; 8];
let (left, _unused) = d.split_at_mut(data.len());
left.clone_from_slice(data);
Some(EspTwaiFrame {
id: id.into(),
data: d,
dlc: data.len(),
is_remote: false,
})
}
fn new_remote(id: impl Into<Id>, dlc: usize) -> Option<Self> {
// CAN2.0 frames cannot have more than 8 bytes.
if dlc > 8 {
return None;
}
Some(EspTwaiFrame {
id: id.into(),
data: [0; 8],
dlc,
is_remote: true,
})
}
fn is_extended(&self) -> bool {
match self.id {
Id::Standard(_) => false,
Id::Extended(_) => true,
}
}
fn is_remote_frame(&self) -> bool {
self.is_remote
}
fn id(&self) -> Id {
self.id
}
fn dlc(&self) -> usize {
self.dlc
}
fn data(&self) -> &[u8] {
// Remote frames do not contain data, yet have a value for the dlc so return
// an empty slice for remote frames.
match self.is_remote_frame() {
true => &[],
false => &self.data[0..self.dlc],
}
}
}
/// The underlying timings for the TWAI peripheral.
pub struct TimingConfig {
pub baud_rate_prescaler: u16,
pub sync_jump_width: u8,
pub tseg_1: u8,
pub tseg_2: u8,
pub triple_sample: bool,
}
/// A selection of pre-determined baudrates for the TWAI driver.
/// Currently these timings are sourced from the ESP IDF C driver which assumes
/// an APB clock of 80MHz.
pub enum BaudRate {
B125K,
B250K,
B500K,
B1000K,
Custom(TimingConfig),
}
impl BaudRate {
/// Convert the BaudRate into the timings that the peripheral needs.
// These timings are copied from the ESP IDF C driver.
// #define TWAI_TIMING_CONFIG_25KBITS() {.brp = 128, .tseg_1 = 16, .tseg_2 =
// 8, .sjw = 3, .triple_sampling = false}
// #define TWAI_TIMING_CONFIG_50KBITS() {.brp = 80, .tseg_1 = 15, .tseg_2 =
// 4, .sjw = 3, .triple_sampling = false}
// #define TWAI_TIMING_CONFIG_100KBITS() {.brp = 40, .tseg_1 = 15, .tseg_2 =
// 4, .sjw = 3, .triple_sampling = false}
// #define TWAI_TIMING_CONFIG_125KBITS() {.brp = 32, .tseg_1 = 15, .tseg_2 =
// 4, .sjw = 3, .triple_sampling = false}
// #define TWAI_TIMING_CONFIG_250KBITS() {.brp = 16, .tseg_1 = 15, .tseg_2 =
// 4, .sjw = 3, .triple_sampling = false}
// #define TWAI_TIMING_CONFIG_500KBITS() {.brp = 8, .tseg_1 = 15, .tseg_2 = 4,
// .sjw = 3, .triple_sampling = false} #define TWAI_TIMING_CONFIG_800KBITS()
// {.brp = 4, .tseg_1 = 16, .tseg_2 = 8, .sjw = 3, .triple_sampling = false}
// #define TWAI_TIMING_CONFIG_1MBITS() {.brp = 4, .tseg_1 = 15, .tseg_2 = 4,
// .sjw = 3, .triple_sampling = false}
const fn timing(self) -> TimingConfig {
match self {
Self::B125K => TimingConfig {
baud_rate_prescaler: 32,
sync_jump_width: 3,
tseg_1: 15,
tseg_2: 4,
triple_sample: false,
},
Self::B250K => TimingConfig {
baud_rate_prescaler: 16,
sync_jump_width: 3,
tseg_1: 15,
tseg_2: 4,
triple_sample: false,
},
Self::B500K => TimingConfig {
baud_rate_prescaler: 8,
sync_jump_width: 3,
tseg_1: 15,
tseg_2: 4,
triple_sample: false,
},
Self::B1000K => TimingConfig {
baud_rate_prescaler: 4,
sync_jump_width: 3,
tseg_1: 15,
tseg_2: 4,
triple_sample: false,
},
Self::Custom(timing_config) => timing_config,
}
}
}
/// An inactive TWAI peripheral in the "Reset"/configuration state.
pub struct TwaiConfiguration<'d, T> {
peripheral: PeripheralRef<'d, T>,
}
impl<'d, T> TwaiConfiguration<'d, T>
where
T: Instance,
{
pub fn new<TX: OutputPin, RX: InputPin>(
peripheral: impl Peripheral<P = T> + 'd,
tx_pin: impl Peripheral<P = TX> + 'd,
rx_pin: impl Peripheral<P = RX> + 'd,
clocks: &Clocks,
baud_rate: BaudRate,
) -> Self {
// Enable the peripheral clock for the TWAI peripheral.
PeripheralClockControl::enable(T::SYSTEM_PERIPHERAL);
// Set up the GPIO pins.
crate::into_ref!(tx_pin, rx_pin);
tx_pin.connect_peripheral_to_output(T::OUTPUT_SIGNAL);
rx_pin.connect_input_to_peripheral(T::INPUT_SIGNAL);
crate::into_ref!(peripheral);
let mut cfg = TwaiConfiguration { peripheral };
cfg.set_baud_rate(baud_rate, clocks);
cfg
}
/// Set the bitrate of the bus.
///
/// Note: The timings currently assume a APB_CLK of 80MHz.
fn set_baud_rate(&mut self, baud_rate: BaudRate, clocks: &Clocks) {
// TWAI is clocked from the APB_CLK according to Table 6-4 [ESP32C3 Reference Manual](https://www.espressif.com/sites/default/files/documentation/esp32-c3_technical_reference_manual_en.pdf)
// Included timings are all for 80MHz so assert that we are running at 80MHz.
assert!(clocks.apb_clock == HertzU32::MHz(80));
// Unpack the baud rate timings and convert them to the values needed for the
// register. Many of the registers have a minimum value of 1 which is
// represented by having zero bits set, therefore many values need to
// have 1 subtracted from them before being stored into the register.
let timing = baud_rate.timing();
let prescale = (timing.baud_rate_prescaler / 2) - 1;
let sjw = timing.sync_jump_width - 1;
let tseg_1 = timing.tseg_1 - 1;
let tseg_2 = timing.tseg_2 - 1;
let triple_sample = timing.triple_sample;
#[cfg(esp32)]
let prescale = prescale as u8;
// Set up the prescaler and sync jump width.
self.peripheral
.register_block()
.bus_timing_0()
.modify(|_, w| {
w.baud_presc()
.variant(prescale)
.sync_jump_width()
.variant(sjw)
});
// Set up the time segment 1, time segment 2, and triple sample.
self.peripheral
.register_block()
.bus_timing_1()
.modify(|_, w| {
w.time_seg1()
.variant(tseg_1)
.time_seg2()
.variant(tseg_2)
.time_samp()
.bit(triple_sample)
});
}
/// Set up the acceptance filter on the device.
///
/// NOTE: On a bus with mixed 11-bit and 29-bit packet id's, you may
/// experience an 11-bit filter match against a 29-bit frame and vice
/// versa. Your application should check the id again once a frame has
/// been received to make sure it is the expected value.
///
/// [ESP32C3 Reference Manual](https://www.espressif.com/sites/default/files/documentation/esp32-c3_technical_reference_manual_en.pdf#subsubsection.29.4.6)
pub fn set_filter(&mut self, filter: impl Filter) {
// Set or clear the rx filter mode bit depending on the filter type.
let filter_mode_bit = filter.filter_type() == FilterType::Single;
self.peripheral
.register_block()
.mode()
.modify(|_, w| w.rx_filter_mode().bit(filter_mode_bit));
// Convert the filter into values for the registers and store them to the
// registers.
let registers = filter.to_registers();
// Copy the filter to the peripheral.
unsafe {
copy_to_data_register(
self.peripheral.register_block().data_0().as_ptr(),
®isters,
);
}
}
/// Set the error warning threshold.
///
/// In the case when any of an error counter value exceeds the threshold, or
/// all the error counter values are below the threshold, an error
/// warning interrupt will be triggered (given the enable signal is
/// valid).
pub fn set_error_warning_limit(&mut self, limit: u8) {
self.peripheral
.register_block()
.err_warning_limit()
.write(|w| w.err_warning_limit().variant(limit));
}
/// Put the peripheral into Operation Mode, allowing the transmission and
/// reception of packets using the new object.
pub fn start(self) -> Twai<'d, T> {
// Put the peripheral into operation mode by clearing the reset mode bit.
self.peripheral
.register_block()
.mode()
.modify(|_, w| w.reset_mode().clear_bit());
Twai {
peripheral: self.peripheral,
}
}
}
/// An active TWAI peripheral in Normal Mode.
///
/// In this mode, the TWAI controller can transmit and receive messages
/// including error signals (such as error and overload frames).
pub struct Twai<'d, T> {
peripheral: PeripheralRef<'d, T>,
}
impl<'d, T> Twai<'d, T>
where
T: Instance,
{
/// Stop the peripheral, putting it into reset mode and enabling
/// reconfiguration.
pub fn stop(self) -> TwaiConfiguration<'d, T> {
// Put the peripheral into reset/configuration mode by setting the reset mode
// bit.
self.peripheral
.register_block()
.mode()
.modify(|_, w| w.reset_mode().set_bit());
TwaiConfiguration {
peripheral: self.peripheral,
}
}
pub fn receive_error_count(&self) -> u8 {
self.peripheral
.register_block()
.rx_err_cnt()
.read()
.rx_err_cnt()
.bits()
}
pub fn transmit_error_count(&self) -> u8 {
self.peripheral
.register_block()
.tx_err_cnt()
.read()
.tx_err_cnt()
.bits()
}
/// Check if the controller is in a bus off state.
pub fn is_bus_off(&self) -> bool {
self.peripheral
.register_block()
.status()
.read()
.bus_off_st()
.bit_is_set()
}
/// Get the number of messages that the peripheral has available in the
/// receive FIFO.
///
/// Note that this may not be the number of valid messages in the receive
/// FIFO due to fifo overflow/overrun.
pub fn num_available_messages(&self) -> u8 {
self.peripheral
.register_block()
.rx_message_cnt()
.read()
.rx_message_counter()
.bits()
}
/// Clear the receive FIFO, discarding any valid, partial, or invalid
/// packets.
///
/// This is typically used to clear an overrun receive FIFO.
///
/// TODO: Not sure if this needs to be guarded against Bus Off or other
/// error states.
pub fn clear_receive_fifo(&self) {
while self.num_available_messages() > 0 {
self.release_receive_fifo();
}
}
/// Release the message in the buffer. This will decrement the received
/// message counter and prepare the next message in the FIFO for
/// reading.
fn release_receive_fifo(&self) {
self.peripheral
.register_block()
.cmd()
.write(|w| w.release_buf().set_bit());
}
}
#[derive(Debug, Copy, Clone, Eq, PartialEq)]
pub enum EspTwaiError {
BusOff,
EmbeddedHAL(ErrorKind),
}
impl Error for EspTwaiError {
fn kind(&self) -> ErrorKind {
match self {
Self::BusOff => ErrorKind::Other,
Self::EmbeddedHAL(kind) => *kind,
}
}
}
/// Copy data from multiple TWAI_DATA_x_REG registers, packing the source into
/// the destination.
///
/// # Safety
/// This function is marked unsafe because it reads arbitrarily from
/// memory-mapped registers. Specifically, this function is used with the
/// TWAI_DATA_x_REG registers which has different results based on the mode of
/// the peripheral.
#[inline(always)]
unsafe fn copy_from_data_register(dest: &mut [u8], src: *const u32) {
for (i, dest) in dest.iter_mut().enumerate() {
// Perform a volatile read to avoid compiler optimizations.
*dest = src.add(i).read_volatile() as u8;
}
}
/// Copy data to multiple TWAI_DATA_x_REG registers, unpacking the source into
/// the destination.
///
/// # Safety
/// This function is marked unsafe because it writes arbitrarily to
/// memory-mapped registers. Specifically, this function is used with the
/// TWAI_DATA_x_REG registers which has different results based on the mode of
/// the peripheral.
#[inline(always)]
unsafe fn copy_to_data_register(dest: *mut u32, src: &[u8]) {
for (i, src) in src.iter().enumerate() {
// Perform a volatile write to avoid compiler optimizations.
dest.add(i).write_volatile(*src as u32);
}
}
impl<T> Can for Twai<'_, T>
where
T: Instance,
{
type Frame = EspTwaiFrame;
type Error = EspTwaiError;
/// Transmit a frame.
///
/// Because of how the TWAI registers are set up, we have to do some
/// assembly of bytes. Note that these registers serve a filter
/// configuration role when the device is in configuration mode so
/// patching the svd files to improve this may be non-trivial.
///
/// [ESP32C3 Reference Manual](https://www.espressif.com/sites/default/files/documentation/esp32-c3_technical_reference_manual_en.pdf#subsubsection.29.4.4.2)
///
/// NOTE: TODO: This may not work if using the self reception/self test
/// functionality. See notes 1 and 2 in the "Frame Identifier" section
/// of the reference manual.
fn transmit(&mut self, frame: &Self::Frame) -> nb::Result<Option<Self::Frame>, Self::Error> {
let status = self.peripheral.register_block().status().read();
// Check that the peripheral is not in a bus off state.
if status.bus_off_st().bit_is_set() {
return nb::Result::Err(nb::Error::Other(EspTwaiError::BusOff));
}
// Check that the peripheral is not already transmitting a packet.
if !status.tx_buf_st().bit_is_set() {
return nb::Result::Err(nb::Error::WouldBlock);
}
// Assemble the frame information into the data_0 byte.
let frame_format: u8 = frame.is_extended() as u8;
let rtr_bit: u8 = frame.is_remote_frame() as u8;
let dlc_bits: u8 = frame.dlc() as u8 & 0b1111;
let data_0: u8 = frame_format << 7 | rtr_bit << 6 | dlc_bits;
self.peripheral
.register_block()
.data_0()
.write(|w| w.tx_byte_0().variant(data_0));
// Assemble the identifier information of the packet.
match frame.id() {
Id::Standard(id) => {
let id = id.as_raw();
self.peripheral
.register_block()
.data_1()
.write(|w| w.tx_byte_1().variant((id >> 3) as u8));
self.peripheral
.register_block()
.data_2()
.write(|w| w.tx_byte_2().variant((id << 5) as u8));
}
Id::Extended(id) => {
let id = id.as_raw();
self.peripheral
.register_block()
.data_1()
.write(|w| w.tx_byte_1().variant((id >> 21) as u8));
self.peripheral
.register_block()
.data_2()
.write(|w| w.tx_byte_2().variant((id >> 13) as u8));
self.peripheral
.register_block()
.data_3()
.write(|w| w.tx_byte_3().variant((id >> 5) as u8));
self.peripheral
.register_block()
.data_4()
.write(|w| w.tx_byte_4().variant((id << 3) as u8));
}
}
// Store the data portion of the packet into the transmit buffer.
if frame.is_data_frame() {
match frame.id() {
Id::Standard(_) => unsafe {
copy_to_data_register(
self.peripheral.register_block().data_3().as_ptr(),
frame.data(),
)
},
Id::Extended(_) => unsafe {
copy_to_data_register(
self.peripheral.register_block().data_5().as_ptr(),
frame.data(),
)
},
}
} else {
// Is RTR frame, so no data is included.
}
// Set the transmit request command, this will lock the transmit buffer until
// the transmission is complete or aborted.
self.peripheral
.register_block()
.cmd()
.write(|w| w.tx_req().set_bit());
// Success in readying packet for transmit. No packets can be replaced in the
// transmit buffer so return None in accordance with the
// embedded-can/embedded-hal trait.
nb::Result::Ok(None)
}
/// Return a received frame if there are any available.
fn receive(&mut self) -> nb::Result<Self::Frame, Self::Error> {
let status = self.peripheral.register_block().status().read();
// Check that the peripheral is not in a bus off state.
if status.bus_off_st().bit_is_set() {
return nb::Result::Err(nb::Error::Other(EspTwaiError::BusOff));
}
// Check that we actually have packets to receive.
if !status.rx_buf_st().bit_is_set() {
return nb::Result::Err(nb::Error::WouldBlock);
}
// Check if the packet in the receive buffer is valid or overrun.
if status.miss_st().bit_is_set() {
return nb::Result::Err(nb::Error::Other(EspTwaiError::EmbeddedHAL(
ErrorKind::Overrun,
)));
}
// Read the frame information and extract the frame id format and dlc.
let data_0 = self
.peripheral
.register_block()
.data_0()
.read()
.tx_byte_0()
.bits();
let is_standard_format = data_0 & 0b1 << 7 == 0;
let is_data_frame = data_0 & 0b1 << 6 == 0;
let dlc = (data_0 & 0b1111) as usize;
// Read the payload from the packet and construct a frame.
let frame = if is_standard_format {
// Frame uses standard 11 bit id.
let data_1 = self
.peripheral
.register_block()
.data_1()
.read()
.tx_byte_1()
.bits();
let data_2 = self
.peripheral
.register_block()
.data_2()
.read()
.tx_byte_2()
.bits();
let raw_id: u16 = ((data_1 as u16) << 3) | ((data_2 as u16) >> 5);
let id = StandardId::new(raw_id).unwrap();
if is_data_frame {
// Create a new frame from the contents of the appropriate TWAI_DATA_x_REG
// registers.
unsafe {
EspTwaiFrame::new_from_data_registers(
id,
self.peripheral.register_block().data_3().as_ptr(),
dlc,
)
}
} else {
EspTwaiFrame::new_remote(id, dlc).unwrap()
}
} else {
// Frame uses extended 29 bit id.
let data_1 = self
.peripheral
.register_block()
.data_1()
.read()
.tx_byte_1()
.bits();
let data_2 = self
.peripheral
.register_block()
.data_2()
.read()
.tx_byte_2()
.bits();
let data_3 = self
.peripheral
.register_block()
.data_3()
.read()
.tx_byte_3()
.bits();
let data_4 = self
.peripheral
.register_block()
.data_4()
.read()
.tx_byte_4()
.bits();
let raw_id: u32 = (data_1 as u32) << 21
| (data_2 as u32) << 13
| (data_3 as u32) << 5
| (data_4 as u32) >> 3;
let id = ExtendedId::new(raw_id).unwrap();
if is_data_frame {
unsafe {
EspTwaiFrame::new_from_data_registers(
id,
self.peripheral.register_block().data_5().as_ptr(),
dlc,
)
}
} else {
EspTwaiFrame::new_remote(id, dlc).unwrap()
}
};
// Release the packet we read from the FIFO, allowing the peripheral to prepare
// the next packet.
self.release_receive_fifo();
nb::Result::Ok(frame)
}
}
pub trait Instance {
const SYSTEM_PERIPHERAL: system::Peripheral;
const INPUT_SIGNAL: InputSignal;
const OUTPUT_SIGNAL: OutputSignal;
fn register_block(&self) -> &RegisterBlock;
}
#[cfg(any(esp32c3, esp32s3))]
impl Instance for crate::peripherals::TWAI0 {
const SYSTEM_PERIPHERAL: system::Peripheral = system::Peripheral::Twai0;
const INPUT_SIGNAL: InputSignal = InputSignal::TWAI_RX;
const OUTPUT_SIGNAL: OutputSignal = OutputSignal::TWAI_TX;
#[inline(always)]
fn register_block(&self) -> &RegisterBlock {
self
}
}
#[cfg(esp32c6)]
impl Instance for crate::peripherals::TWAI0 {
const SYSTEM_PERIPHERAL: system::Peripheral = system::Peripheral::Twai0;
const INPUT_SIGNAL: InputSignal = InputSignal::TWAI0_RX;
const OUTPUT_SIGNAL: OutputSignal = OutputSignal::TWAI0_TX;
#[inline(always)]
fn register_block(&self) -> &RegisterBlock {
self
}
}
#[cfg(esp32c6)]
impl Instance for crate::peripherals::TWAI1 {
const SYSTEM_PERIPHERAL: system::Peripheral = system::Peripheral::Twai1;
const INPUT_SIGNAL: InputSignal = InputSignal::TWAI1_RX;
const OUTPUT_SIGNAL: OutputSignal = OutputSignal::TWAI1_TX;
#[inline(always)]
fn register_block(&self) -> &RegisterBlock {
self
}
}