186
32072H–AVR32–10/2012
AT32UC3A3
Figure 15-8. No Setup, No Hold on NRD, and NCS Read Signals
• Null Pulse
Programming null pulse is not permitted. Pulse must be at least written to one. A null value leads
to unpredictable behavior.
15.6.4.2
Read mode
As NCS and NRD waveforms are defined independently of one other, the SMC needs to know
when the read data is available on the data bus. The SMC does not compare NCS and NRD tim-
i n g s t o k n o w w h i c h s i g n a l r i s e s f i r s t . T h e R e a d M o d e b i t i n t h e M O D E r e g i s t e r
(MODE.READMODE) of the corresponding chip select indicates which signal of NRD and NCS
controls the read operation.
•Read is controlled by NRD (MODE.READMODE = 1)
shows the waveforms of a read operation of a typical asynchronous
RAM. The read data is available t
PACC
after the falling edge of NRD, and turns to ‘Z’ after the ris-
ing edge of NRD. In this case, the MODE.READMODE bit must be written to one (read is
controlled by NRD), to indicate that data is available with the rising edge of NRD. The SMC sam-
ples the read data internally on the rising edge of CLK_SMC that generates the rising edge of
NRD, whatever the programmed waveform of NCS may be.
CLK_SMC
A[AD_MSB:2]
NBS0, NBS1,
A0, A1
NRD
NCS
D[15:0]
NRDSETUP
NRDPULSE
NCSRDPULSE
NRDCYCLE
NRDCYCLE
NCSRDPULSE
NCSRDPULSE
NRDPULSE
NRDCYCLE
Содержание AT32UC3A3128
Страница 61: ...61 32072H AVR32 10 2012 AT32UC3A3 PLLEN PLL Enable 0 PLL is disabled 1 PLL is enabled...
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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...