Datasheet

209
SAM9G45 [DATASHEET]
Atmel-6438O-ATARM-SAM9G45-Datasheet_08-Dec-15
20.11.2 Frozen Mode
When the external device asserts the NWAIT signal (active low), and after internal synchronization of this signal,
the SMC state is frozen, i.e., SMC internal counters are frozen, and all control signals remain unchanged. When
the resynchronized NWAIT signal is deasserted, the SMC completes the access, resuming the access from the
point where it was stopped. See Figure 20-26. This mode must be selected when the external device uses the
NWAIT signal to delay the access and to freeze the SMC.
The assertion of the NWAIT signal outside the expected period is ignored as illustrated in Figure 20-27.
Figure 20-26. Write Access with NWAIT Assertion in Frozen Mode (EXNW_MODE = 10)
EXNW_MODE = 10 (Frozen)
WRITE_MODE = 1 (NWE_controlled)
NWE_PULSE = 5
NCS_WR_PULSE = 7
A
[25:2]
MCK
NWE
NCS
432 1 1101
4563222210
Write cycle
D[31:0]
NWAIT
FROZEN STATE
NBS0, NBS1,
NBS2, NBS3,
A0,A1
internally synchronized
NWAIT signal