Datasheet

335
32117D–AVR-01/12
AT32UC3C
18.6.7.4 NWAIT latency and read/write timings
There may be a latency between the assertion of the read/write controlling signal and the asser-
tion of the NWAIT signal by the device. The programmed pulse length of the read/write
controlling signal must be at least equal to this latency plus the two cycles of resynchronization
plus one cycle. Otherwise, the SMC may enter the hold state of the access without detecting the
NWAIT signal assertion. This is true in frozen mode as well as in ready mode. This is illustrated
on Figure 18-29 on page 335.
When the MODE.EXNWMODE field is enabled (ready or frozen), the user must program a pulse
length of the read and write controlling signal of at least:
Figure 18-29. NWAIT Latency
minimal pulse length NWAIT latency 2 synchronization cycles 1 cycle++=
Wait STATE
012
3
4
CLK_SMC
A[AD_MSB:2]
NBS0, NBS1,
A0, A1
NRD
NWAIT
nternally synchronized
NWAIT signal
Minimal pulse length
00
NWAIT latency 2 cycle resynchronization
Read cycle
EXNWMODE = 2 or 3
READMODE = 1 (NRD controlled)
NRDPULSE = 5