Transactions

Forastero expects drivers and monitors to consume or produce a standard form of transaction that is based on Python's dataclasses library. A custom base class (BaseTransaction) is provided that helps Forastero interact with these components.

For example, a transaction for driving requests on an address mapped interface to a memory may look something like the following:

tb/mapped/transaction.py

import dataclasses
from enum import IntEnum, auto

from forastero import BaseTransaction

class MappedAccess(IntEnum):
    READ  = auto()
    WRITE = auto()

@dataclasses.dataclass(kw_only=True)
class MappedRequest(BaseTransaction):
    address : int = 0
    access  : MappedAccess = MappedAccess.READ
    data    : int = 0

The MappedRequest transaction is decorated by dataclass to mark it as a dataclass object (see the Python documentation for more details), but importantly also inherits from BaseTransaction. This base class provides a standard entry called timestamp that is used to capture when the transaction was submitted to or captured from the design, it is excluded from comparisons and exists primarily for debug.

---

forastero.transaction.BaseTransaction dataclass

Base transaction object type

Parameters:

Name	Type	Description	Default
timestamp	int	The time at which the event occurred	lambda: get_sim_time(units='ns')()
_f_event	Enum | None	Forastero event type to trigger on	None
_c_event	Event | None	The cocotb Event to trigger when _f_event is reached	None

format(field, value)

Subclasses of BaseTransaction may override this to format different fields however they prefer.

Parameters:

Name	Type	Description	Default
field	str	Name of the field to format	required
value	Any	Value to format	required

Returns:

Type	Description
str	A string of the formatted value

tabulate(other=None)

Tabulate the fields of this transaction, optionally comparing against the fields of another object of this same type. When comparison is performed, mismatches are flagged in a separate column.

Parameters:

Name	Type	Description	Default
other	Optional[BaseTransaction]	Optional transaction to compare against	None

Returns:

Type	Description
str	String of tabulated data