404
11054A–ATARM–27-Jul-11
SAM9X25
404
11054A–ATARM–27-Jul-11
SAM9X25
29.12.4
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 2 cycles of resynchroni 1
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
When EXNW_MODE is enabled (ready or frozen), the user must program a pulse length of the
read and write controlling signal of at least:
minimal pulse length = NWAIT l 2 resynchronization 1 cycle
Figure 29-30.
NWAIT Latency
EXNW_MODE = 10 or 11
READ_MODE = 1 (NRD_controlled)
NRD_PULSE = 5
A
[25:2]
MCK
NRD
4
3
2
1
0
0
0
Read cycle
minimal pulse length
NWAIT latency
NWAIT
intenally synchronized
NWAIT signal
WAIT STATE
2 cycle resynchronization
NBS0, NBS1,
NBS2, NBS3,
A0,A1
Содержание SAM9X25
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