Atmel Xplained Evaluation Board AT32UC3A3-XPLD AT32UC3A3-XPLD 数据表

32072H–AVR32–10/2012

Figure 15-18. Early Read Wait State: NWE-controlled Write with No Hold Followed by a Read 

with one Set-up Cycle. 

The user may change any of the configuration parameters by writing the SMC user interface. 

When detecting that a new user configuration has been written in the user interface, the SMC
inserts a wait state before starting the next access. The so called “reload user configuration wait
state” is used by the SMC to load the new set of parameters to apply to next accesses.

The reload configuration wait state is not applied in addition to the chip select wait state. If
accesses before and after reprogramming the user interface are made to different devices (dif-
ferent chip selects), then one single chip select wait state is applied.

On the other hand, if accesses before and after writing the user interface are made to the same
device, a reload configuration wait state is inserted, even if the change does not concern the cur-
rent chip select.

To insert a reload configuration wait state, the SMC detects a write access to any MODE register
of the user interface. If the user only modifies timing registers (SETUP, PULSE, CYCLE regis-
ters) in the user interface, he must validate the modification by writing the MODE register, even
if no change was made on the mode parameters.

CLK_SMC

A[AD_MSB:2]

NBS0, NBS1, 

A0, A1

Internal write controlling signal

external write controlling 

signal(NWE)

NRD

D[15:0]

No hold

Read setup=1

Write cycle

(WRITEMODE = 1)

Early Read

Wait State

Read cycle

(READMODE=0 or READMODE=1)