157 lines
5.6 KiB
Python
157 lines
5.6 KiB
Python
from __future__ import annotations
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from dataclasses import dataclass
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from typing import Iterable
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P9_ACK_BIT = 0x80
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P9_STROBE_BIT = 0x02
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@dataclass(frozen=True)
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class P9StrobeEvent:
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edge: str
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ddr: int
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dr: int
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data_bit: int
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bit7_output: bool
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@dataclass(frozen=True)
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class P9TraceEvent:
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kind: str
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ddr: int
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dr: int
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value: int | None = None
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bit: int | None = None
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source: str | None = None
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success: bool | None = None
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queue_depth: int | None = None
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def line(self) -> str:
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parts = [self.kind, f"ddr={self.ddr:02X}", f"dr={self.dr:02X}"]
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if self.value is not None:
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parts.append(f"value={self.value:02X}")
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if self.bit is not None:
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parts.append(f"bit={self.bit}")
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if self.success is not None:
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parts.append(f"success={int(self.success)}")
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if self.source is not None:
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parts.append(f"source={self.source}")
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if self.queue_depth is not None:
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parts.append(f"queued={self.queue_depth}")
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return " ".join(parts)
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class P9Bus:
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"""Small model for the ROM's P9 bit-banged serial handshake."""
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def __init__(
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self,
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ddr: int = 0x00,
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dr: int = 0x00,
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input_bits: Iterable[int] = (),
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wrapper_results: Iterable[bool] = (),
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) -> None:
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self.ddr = ddr & 0xFF
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self.dr_latch = dr & 0xFF
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self.input_bits: list[int] = [1 if bit else 0 for bit in input_bits]
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self.default_input_bit = 0
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self.wrapper_results: list[bool] = [bool(result) for result in wrapper_results]
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self.wrapper_sources: list[str] = ["initial"] * len(self.wrapper_results)
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self.default_wrapper_success = False
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self.strobe_edges: list[P9StrobeEvent] = []
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self.trace_events: list[P9TraceEvent] = []
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self.transmitted_bits: list[int] = []
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self.byte_candidates: list[int] = []
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def write_ddr(self, value: int) -> int:
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self.ddr = value & 0xFF
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self.trace_events.append(P9TraceEvent("write_ddr", self.ddr, self.dr_latch, value=self.ddr))
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return self.ddr
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def write_dr(self, value: int) -> int:
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previous = self.dr_latch
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self.dr_latch = value & 0xFF
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self.trace_events.append(P9TraceEvent("write_dr", self.ddr, self.dr_latch, value=self.dr_latch))
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previous_strobe = bool(previous & P9_STROBE_BIT)
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current_strobe = bool(self.dr_latch & P9_STROBE_BIT)
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if previous_strobe != current_strobe:
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edge = "rising" if current_strobe else "falling"
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data_bit = 1 if self.dr_latch & P9_ACK_BIT else 0
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bit7_output = bool(self.ddr & P9_ACK_BIT)
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self.strobe_edges.append(P9StrobeEvent(edge, self.ddr, self.dr_latch, data_bit, bit7_output))
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self.trace_events.append(P9TraceEvent(f"strobe_{edge}", self.ddr, self.dr_latch, bit=data_bit))
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if edge == "rising" and bit7_output:
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self._record_transmitted_bit(data_bit)
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return self.dr_latch
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def read_ddr(self) -> int:
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return self.ddr
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def read_dr(self) -> int:
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value = self.dr_latch
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input_bit = None
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source = None
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if not (self.ddr & P9_ACK_BIT):
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if self.input_bits:
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input_bit = self.input_bits.pop(0)
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source = "queued_bit"
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else:
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input_bit = self.default_input_bit
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source = "default_bit"
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if input_bit:
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value |= P9_ACK_BIT
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else:
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value &= ~P9_ACK_BIT
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self.trace_events.append(P9TraceEvent("read_dr", self.ddr, value & 0xFF, value=value, bit=input_bit, source=source))
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return value & 0xFF
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def queue_input_bits(self, bits: Iterable[int]) -> None:
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self.input_bits.extend(1 if bit else 0 for bit in bits)
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def set_default_input_bit(self, bit: int) -> None:
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self.default_input_bit = 1 if bit else 0
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def queue_wrapper_results(self, results: Iterable[bool], source: str = "queued_wrapper") -> None:
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for result in results:
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self.wrapper_results.append(bool(result))
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self.wrapper_sources.append(source)
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def consume_wrapper_result(self) -> tuple[bool, str, int]:
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if self.wrapper_results:
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success = self.wrapper_results.pop(0)
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source = self.wrapper_sources.pop(0) if self.wrapper_sources else "queued_wrapper"
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else:
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success = self.default_wrapper_success
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source = "default_success" if success else "default_timeout"
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queue_depth = len(self.wrapper_results)
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self.trace_events.append(
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P9TraceEvent(
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"wrapper_result",
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self.ddr,
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self.dr_latch,
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value=1 if success else 0,
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success=success,
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source=source,
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queue_depth=queue_depth,
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)
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)
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return success, source, queue_depth
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def trace_lines(self, limit: int | None = None) -> list[str]:
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events = self.trace_events if limit is None else self.trace_events[-limit:]
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return [event.line() for event in events]
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def _record_transmitted_bit(self, bit: int) -> None:
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self.transmitted_bits.append(bit)
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self.trace_events.append(P9TraceEvent("tx_bit", self.ddr, self.dr_latch, bit=bit))
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if len(self.transmitted_bits) % 8 == 0:
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byte = 0
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for data_bit in self.transmitted_bits[-8:]:
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byte = (byte << 1) | data_bit
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self.byte_candidates.append(byte)
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self.trace_events.append(P9TraceEvent("tx_byte", self.ddr, self.dr_latch, value=byte))
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