193
32072H–AVR32–10/2012
AT32UC3A3
15.6.5
Automatic Wait States
Under certain circumstances, the SMC automatically inserts idle cycles between accesses to
avoid bus contention or operation conflict.
15.6.5.1
Chip select wait states
The SMC always inserts an idle cycle between two transfers on separate chip selects. This idle
cycle ensures that there is no bus contention between the deactivation of one device and the
activation of the next one.
During chip select wait state, all control lines are turned inactive: NBS0 to NBS3, NWR0 to
NWR3, NCS[0..5], NRD lines are all set to high level.
illustrates a chip select wait state between access on Chip Select 0
(NCS0) and Chip Select 2 (NCS2).
Figure 15-15. Chip Select Wait State Between a Read Access on NCS0 and a Write Access on
NCS2
15.6.5.2
Early read wait state
In some cases, the SMC inserts a wait state cycle between a write access and a read access to
allow time for the write cycle to end before the subsequent read cycle begins. This wait state is
not generated in addition to a chip select wait state. The early read cycle thus only occurs
between a write and read access to the same memory device (same chip select).
CLK_SMC
_MSB:2]
, NBS1,
, A1
NRD
NWE
NCS0
NCS2
D[15:0]
NRDCYCLE
Read to Write
Wait State
Chip Select
Wait State
NWECYCLE
Содержание AT32UC3A3128
Страница 61: ...61 32072H AVR32 10 2012 AT32UC3A3 PLLEN PLL Enable 0 PLL is disabled 1 PLL is enabled...
Страница 260: ...260 32072H AVR32 10 2012 AT32UC3A3 5 2560 3071 6 3072 3583 7 3584 4095 Bit Index n Sector Boundaries...
Страница 592: ...592 32072H AVR32 10 2012 AT32UC3A3 Manchester Configuration Register on page 614...
Страница 989: ...989 32072H AVR32 10 2012 AT32UC3A3 37 2 Package Drawings Figure 37 1 TFBGA 144 package drawing...
Страница 991: ...991 32072H AVR32 10 2012 AT32UC3A3 Figure 37 3 VFBGA 100 package drawing...