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##
## This file is part of the libsigrokdecode project.
##
## Copyright (C) 2018 fenugrec <fenugrec@users.sourceforge.net>
##
## This program is free software; you can redistribute it and/or modify
## it under the terms of the GNU General Public License as published by
## the Free Software Foundation; either version 2 of the License, or
## (at your option) any later version.
##
## This program is distributed in the hope that it will be useful,
## but WITHOUT ANY WARRANTY; without even the implied warranty of
## MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
## GNU General Public License for more details.
##
## You should have received a copy of the GNU General Public License
## along with this program; if not, see <http://www.gnu.org/licenses/>.
##
import sigrokdecode as srd
class ChannelError(Exception):
pass
class Decoder(srd.Decoder):
api_version = 3
id = 'mcs48'
name = 'MCS-48'
longname = 'Intel MCS-48'
desc = 'Intel MCS-48 external memory access protocol.'
license = 'gplv2+'
inputs = ['logic']
outputs = []
tags = ['Retro computing']
channels = (
{'id': 'ale', 'name': 'ALE', 'desc': 'Address latch enable'},
{'id': 'psen', 'name': '/PSEN', 'desc': 'Program store enable'},
) + tuple({
'id': 'd%d' % i,
'name': 'D%d' % i,
'desc': 'CPU data line %d' % i
} for i in range(0, 8)
) + tuple({
'id': 'a%d' % i,
'name': 'A%d' % i,
'desc': 'CPU address line %d' % i
} for i in range(8, 12)
)
optional_channels = tuple({
'id': 'a%d' % i,
'name': 'A%d' % i,
'desc': 'CPU address line %d' % i
} for i in range(12, 13)
)
annotations = (
('romdata', 'Address:Data'),
)
binary = (
('romdata', 'AAAA:DD'),
)
OFF_ALE, OFF_PSEN = 0, 1
OFF_DATA_BOT, OFF_DATA_TOP = 2, 10
OFF_ADDR_BOT, OFF_ADDR_TOP = 10, 14
OFF_BANK_BOT, OFF_BANK_TOP = 14, 15
def __init__(self):
self.reset()
def reset(self):
self.addr = 0
self.addr_s = 0
self.data = 0
self.data_s = 0
# Flag to make sure we get an ALE pulse first.
self.started = 0
def start(self):
self.out_ann = self.register(srd.OUTPUT_ANN)
self.out_bin = self.register(srd.OUTPUT_BINARY)
def newaddr(self, addr, data):
# Falling edge on ALE: reconstruct address.
self.started = 1
addr = sum([bit << i for i, bit in enumerate(addr)])
addr <<= len(data)
addr |= sum([bit << i for i, bit in enumerate(data)])
self.addr = addr
self.addr_s = self.samplenum
def newdata(self, data):
# Edge on PSEN: get data.
data = sum([bit << i for i, bit in enumerate(data)])
self.data = data
self.data_s = self.samplenum
if self.started:
anntext = '{:04X}:{:02X}'.format(self.addr, self.data)
self.put(self.addr_s, self.data_s, self.out_ann, [0, [anntext]])
bindata = self.addr.to_bytes(2, byteorder='big')
bindata += self.data.to_bytes(1, byteorder='big')
self.put(self.addr_s, self.data_s, self.out_bin, [0, bindata])
def decode(self):
# Address bits above A11 are optional, and are considered to be A12+.
# This logic needs more adjustment when more bank address pins are
# to get supported. For now, having just A12 is considered sufficient.
has_bank = self.has_channel(self.OFF_BANK_BOT)
bank_pin_count = 1 if has_bank else 0
# Sample address on the falling ALE edge.
# Save data on falling edge of PSEN.
while True:
pins = self.wait([{self.OFF_ALE: 'f'}, {self.OFF_PSEN: 'r'}])
data = pins[self.OFF_DATA_BOT:self.OFF_DATA_TOP]
addr = pins[self.OFF_ADDR_BOT:self.OFF_ADDR_TOP]
bank = pins[self.OFF_BANK_BOT:self.OFF_BANK_TOP]
if has_bank:
addr += bank[:bank_pin_count]
# Handle those conditions (one or more) that matched this time.
if self.matched[0]:
self.newaddr(addr, data)
if self.matched[1]:
self.newdata(data)
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