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280 lines
8.9 KiB
C++
280 lines
8.9 KiB
C++
//
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// TargetImplementation.hpp
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// Clock Signal
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//
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// Created by Thomas Harte on 19/08/2019.
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// Copyright © 2019 Thomas Harte. All rights reserved.
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//
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#pragma once
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template <typename Executor> Target<Executor>::Target(Bus &bus, int scsi_id) :
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bus_(bus),
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scsi_id_mask_(BusState(1 << scsi_id)),
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scsi_bus_device_id_(bus.add_device()) {
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bus.add_observer(this);
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}
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template <typename Executor> void Target<Executor>::scsi_bus_did_change(Bus *, BusState new_state, double time_since_change) {
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/*
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"The target determines that it is selected when the SEL# signal
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and its SCSI ID bit are active and the BSY# and I#/O signals
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are false. It then asserts the signal within a selection
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abort time."
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*/
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// Wait for deskew, at the very least.
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if(time_since_change < SCSI::DeskewDelay) return;
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// A reset always takes precedence over anything else ongoing.
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if(new_state & Line::Reset) {
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phase_ = Phase::AwaitingSelection;
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bus_state_ = DefaultBusState;
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set_device_output(bus_state_);
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return;
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}
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switch(phase_) {
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/*
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While awaiting selection the SCSI target is passively watching the bus waiting for its ID
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to be set during a target selection. It will segue automatically from there to the command
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phase regardless of its executor.
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*/
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case Phase::AwaitingSelection:
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if(
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(new_state & scsi_id_mask_) &&
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((new_state & (Line::SelectTarget | Line::Busy | Line::Input)) == Line::SelectTarget)
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) {
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phase_ = Phase::Command;
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command_.resize(0);
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command_pointer_ = 0;
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bus_state_ |= Line::Busy; // Initiate the command phase: request a command byte.
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set_device_output(bus_state_);
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}
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break;
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/*
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In the command phase, the target will stream an appropriate number of bytes for the command
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it is being offered, before giving the executor a chance to handle the command. If the target
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supports this command, it becomes responsible for the appropriate next phase transition. If it
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reports that it doesn't support that command, a suitable response is automatically dispatched.
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*/
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case Phase::Command:
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// Wait for select to be disabled before beginning the control phase proper.
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if((new_state & Line::SelectTarget)) return;
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bus_state_ |= Line::Control;
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switch(new_state & (Line::Request | Line::Acknowledge)) {
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// If request and acknowledge are both enabled, grab a byte and cancel the request.
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case Line::Request | Line::Acknowledge:
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bus_state_ &= ~Line::Request;
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if(command_.empty()) {
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begin_command(uint8_t(new_state));
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// TODO: if(command_.empty()) signal_error_somehow();
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} else {
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command_[command_pointer_] = uint8_t(new_state);
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++command_pointer_;
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if(command_pointer_ == command_.size()) {
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if(!dispatch_command()) {
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// This is just a guess for now; I don't know how SCSI
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// devices are supposed to respond if they don't support
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// a command.
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terminate_command(Responder::Status::TaskAborted);
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}
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}
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}
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break;
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// The reset of request has caused the initiator to reset acknowledge, so it is now
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// safe to request the next byte.
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case 0:
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bus_state_ |= Line::Request;
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break;
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default: break;
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}
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set_device_output(bus_state_);
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break;
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case Phase::ReceivingData:
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switch(new_state & (Line::Request | Line::Acknowledge)) {
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case Line::Request | Line::Acknowledge:
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bus_state_ &= ~Line::Request;
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data_[data_pointer_] = uint8_t(new_state);
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++data_pointer_;
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break;
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case 0:
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if(data_pointer_ == data_.size()) {
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next_function_(CommandState(command_, data_), *this);
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} else {
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bus_state_ |= Line::Request;
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}
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break;
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}
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set_device_output(bus_state_);
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break;
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case Phase::SendingData:
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case Phase::SendingStatus:
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case Phase::SendingMessage:
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switch(new_state & (Line::Request | Line::Acknowledge)) {
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case Line::Request | Line::Acknowledge:
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bus_state_ &= ~(Line::Request | 0xff);
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++data_pointer_;
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break;
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case 0:
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if(
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(phase_ == Phase::SendingMessage && data_pointer_ == 1) ||
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(phase_ == Phase::SendingStatus && data_pointer_ == 1) ||
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(phase_ == Phase::SendingData && data_pointer_ == data_.size())
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) {
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next_function_(CommandState(command_, data_), *this);
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} else {
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bus_state_ |= Line::Request;
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bus_state_ &= ~0xff;
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switch(phase_) {
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case Phase::SendingData: bus_state_ |= data_[data_pointer_]; break;
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case Phase::SendingStatus: bus_state_ |= BusState(status_); break;
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default:
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case Phase::SendingMessage: bus_state_ |= BusState(message_); break;
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}
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}
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break;
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}
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set_device_output(bus_state_);
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break;
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}
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}
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template <typename Executor> void Target<Executor>::begin_command(uint8_t first_byte) {
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// The logic below is valid for SCSI-1. TODO: other SCSIs.
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switch(first_byte >> 5) {
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default: break;
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case 0: command_.resize(6); break; // Group 0 commands: 6 bytes long.
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case 1: command_.resize(10); break; // Group 1 commands: 10 bytes long.
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case 5: command_.resize(12); break; // Group 5 commands: 12 bytes long.
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}
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// Store the first byte if it was recognised.
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if(!command_.empty()) {
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command_[0] = first_byte;
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command_pointer_ = 1;
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}
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}
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namespace {
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constexpr uint8_t G0(uint8_t opcode) { return 0x00 | opcode; }
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constexpr uint8_t G1(uint8_t opcode) { return 0x20 | opcode; }
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constexpr uint8_t G5(uint8_t opcode) { return 0xa0 | opcode; }
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}
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template <typename Executor> bool Target<Executor>::dispatch_command() {
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CommandState arguments(command_, data_);
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log_.info().append("---Command %02x---", command_[0]);
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switch(command_[0]) {
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default: return false;
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case G0(0x00): return executor_.test_unit_ready(arguments, *this);
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case G0(0x01): return executor_.rezero_unit(arguments, *this);
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case G0(0x03): return executor_.request_sense(arguments, *this);
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case G0(0x04): return executor_.format_unit(arguments, *this);
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case G0(0x08): return executor_.read(arguments, *this);
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case G0(0x0a): return executor_.write(arguments, *this);
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case G0(0x0b): return executor_.seek(arguments, *this);
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case G0(0x12): return executor_.inquiry(arguments, *this);
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case G0(0x15): return executor_.mode_select(arguments, *this);
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case G0(0x16): return executor_.reserve_unit(arguments, *this);
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case G0(0x17): return executor_.release_unit(arguments, *this);
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case G0(0x1a): return executor_.mode_sense(arguments, *this);
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case G0(0x1c): return executor_.read_diagnostic(arguments, *this);
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case G0(0x1d): return executor_.write_diagnostic(arguments, *this);
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case G1(0x05): return executor_.read_capacity(arguments, *this);
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case G1(0x08): return executor_.read(arguments, *this);
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case G1(0x0a): return executor_.write(arguments, *this);
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case G1(0x0e): return executor_.write_and_verify(arguments, *this);
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case G1(0x0f): return executor_.verify(arguments, *this);
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case G1(0x11): return executor_.search_data_equal(arguments, *this);
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case G1(0x10): return executor_.search_data_high(arguments, *this);
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case G1(0x12): return executor_.search_data_low(arguments, *this);
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case G1(0x1c): return executor_.read_buffer(arguments, *this);
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case G1(0x15): return executor_.mode_select(arguments, *this);
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case G5(0x09): return executor_.set_block_limits(arguments, *this);
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}
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return false;
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}
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template <typename Executor> void Target<Executor>::send_data(std::vector<uint8_t> &&data, continuation next) {
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// Data out phase: control and message all reset, input set.
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bus_state_ &= ~(Line::Control | Line::Input | Line::Message);
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bus_state_ |= Line::Input;
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phase_ = Phase::SendingData;
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next_function_ = next;
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data_ = std::move(data);
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data_pointer_ = 0;
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set_device_output(bus_state_);
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}
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template <typename Executor> void Target<Executor>::receive_data(size_t length, continuation next) {
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// Data out phase: control, input and message all reset.
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bus_state_ &= ~(Line::Control | Line::Input | Line::Message);
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phase_ = Phase::ReceivingData;
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next_function_ = next;
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data_.resize(length);
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data_pointer_ = 0;
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set_device_output(bus_state_);
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}
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template <typename Executor> void Target<Executor>::send_status(Status status, continuation next) {
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// Status phase: message reset, control and input set.
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bus_state_ &= ~(Line::Control | Line::Input | Line::Message);
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bus_state_ |= Line::Input | Line::Control;
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status_ = status;
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phase_ = Phase::SendingStatus;
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next_function_ = next;
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data_pointer_ = 0;
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set_device_output(bus_state_);
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}
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template <typename Executor> void Target<Executor>::send_message(Message message, continuation next) {
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// Message in phase: message, control and input set.
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bus_state_ |= Line::Message | Line::Control | Line::Input;
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message_ = message;
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phase_ = Phase::SendingMessage;
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next_function_ = next;
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data_pointer_ = 0;
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set_device_output(bus_state_);
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}
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template <typename Executor> void Target<Executor>::end_command() {
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// TODO: was this a linked command?
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// Release all bus lines and return to awaiting selection.
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phase_ = Phase::AwaitingSelection;
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bus_state_ = DefaultBusState;
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set_device_output(bus_state_);
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log_.info().append("---Done---");
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}
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