BYTEBUS reads or writes
the 8 bit + 2 control lines on Port1 of the LPC2138. The control
field sets the state
of the 2 control lines, with the intention of
line 0 being used as a R/W line and line 1 being used as a
CS line-
0 -- set control line 0 low, and pulse line 1 low
1 -- set control line 0 high, and pulse line 1 low
2 -- set control line 0 low, and pulse line 1 high
3 -- set control line 0 high, and
pulse line 1 high
4 -- use the 10 lines as a block of inputs or outputs (added in version 7 firmware)
For 0-3:
The pulsewidth on line 1 is 250 nsec for write, and 550 nsec for read.
Back to back operations occur 2.4 usec apart for writes, 2 usec for read.
None of these lines are driven on reset, and should be biased with resistors if devices connected to this bus require it.