Atmel SAM4S-EK2 Atmel ATSAM4S-EK2 ATSAM4S-EK2 Data Sheet

 415

SAM4S [DATASHEET]

11100E–ATARM–24-Jul-13

In Ready mode (EXNW_MODE = 11), the SMC behaves differently. Normally, the SMC begins the access by down
counting the setup and pulse counters of the read/write controlling signal. In the last cycle of the pulse phase, the
resynchronized NWAIT signal is examined. 

If asserted, the SMC suspends the access as shown in 

completed: the hold step of the access is performed.

This mode must be selected when the external device uses deassertion of the NWAIT signal to indicate its ability to
complete the read or write operation.

If the NWAIT signal is deasserted before the end of the pulse, or asserted after the end of the pulse of the controlling
read/write signal, it has no impact on the access length as shown in 

.

EXNW_MODE = 11 (Ready mode)
WRITE_MODE = 1 (NWE_controlled)

NWE_PULSE = 5
NCS_WR_PULSE = 7

A[23:0]

MCK

NWE

NCS

4

3

2

1

0

0

0

4

5

6

3

2

1

1

1

0

Write cycle

D[7:0]

NWAIT

internally synchronized

NWAIT signal

Wait  STATE