Top secrets sources NedoPC zxusbnet

clk=48mhz
cpu=3.5..14mhz (nowait)

'start access' signal -- max 4tc after combinatorial read/write from host

->D->D->D\
      |  |
      \--L->start access
old------^
state

access time for both sl811 and w5300 -- 5tc

data setup for w5300: 42ns
data setup for sl811: 25..85ns


READ: via latch, transparent during access time, then latches read data (if CPU cycle continues)

WRITE: via latch, data latched from CPU early, shown to the peripherals for the 5 tc
 -- ACHTUNG write /WR strobe is late!!!111

5tc@48MHz = 1.5 tc @ 14MHz
4tc@48MHz = 1.2 tc @ 14MHz
so write will finish after 2.7 tc @ 14MHz after write pulse begin (memory write),
such write WON'T coincide with the following memory read cycle, because it can't start earlier than
3tc @48MHz after read pulse



TODO:
 + забуферировать rd/wr
 + забуферировать cs's
 + забуферировать sl811_a0
 + забуферировать w5300_a
 + сделать новое управление шиной