SAM3X8E Atmel Corporation, SAM3X8E Datasheet - Page 450

• Manufacturer Part Number: SAM3X8E
• Manufacturer: Atmel Corporation

26.13.1
450
450
SAM3X/A
SAM3X/A
READ_MODE
Setting READ_MODE to 1 indicates to the SMC that the NRD signal is responsible for turning off
the tri-state buffers of the external memory device. The Data Float Period then begins after the
rising edge of the NRD signal and lasts TDF_CYCLES MCK cycles.
When the read operation is controlled by the NCS signal (READ_MODE = 0), the TDF field gives
the number of MCK cycles during which the data bus remains busy after the rising edge of NCS.
Figure 26-17
assuming a data float period of 2 cycles (TDF_CYCLES = 2).
ation when controlled by NCS (READ_MODE = 0) and the TDF_CYCLES parameter equals 3.
Figure 26-17. TDF Period in NRD Controlled Read Access (TDF = 2)
NBS0, NBS1,
illustrates the Data Float Period in NRD-controlled mode (READ_MODE =1),
A[23:2]
D[15:0]
A0, A1
MCK
NRD
NCS
NRD controlled read operation
tpacc
TDF = 2 clock cycles
Figure 26-18
shows the read oper-
11057A–ATARM–17-Feb-12
11057A–ATARM–17-Feb-12