Atmel Xplained Pro Evaluation Kit ATSAM4E-XPRO ATSAM4E-XPRO Data Sheet
Product codes
ATSAM4E-XPRO
553
SAM4E [DATASHEET]
Atmel-11157D-ATARM-SAM4E16-SAM4E8-Datasheet_12-Jun-14
28.12.4 NWAIT Latency and Read/Write Timings
There may be a latency between the assertion of the read/write controlling signal and the assertion 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 resynchronization + 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
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 resynchronization + 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:
controlling signal of at least:
minimal pulse length = NWAIT latency + 2 resynchronization cycles + 1 cycle
Figure 28-27. NWAIT Latency
EXNW_MODE = 10 or 11
READ_MODE = 1 (NRD_controlled)
READ_MODE = 1 (NRD_controlled)
NRD_PULSE = 5
A[23:0]
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