Toshiba TX49 TMPR4937, Руководство пользователя

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Chapter 7 External Bus Controller
7-24
7.5
Timing Diagrams
Please take the following points into account when referring to the timing diagrams.
(1) The clock frequency of the SYSCLK signal can be set to one of the following divisions of the internal
bus clock (GBUSCLK): 1/1, 1/2, 1/3, or 1/4. Also, the operating reference clock frequency can be set to
one of the following divisions of the internal bus clock (GBUSCLK) for each channel: 1/1, 1/2, 1/3, or
1/4. (See 7.3.8.) The timing diagrams indicate the SYSCLK signal clock frequency and channel
operating reference clock frequency as being equivalent.
(2) Both the BWE* signal and BE* signal are indicated in all timing diagrams. The setting of the Channel
Control Register (EBCCRn) determines whether the BWE* pin will function as BWE* or BE*.
(3) All Burst cycles in the timing diagrams illustrate examples in which the address increases by increments
of 1 starting from 0. However, cases where the CWF (Critical Word First) function of the TX49 core
was used or the decrement burst function performed by the DMA Controller was used are exceptions.
(4) The timing diagrams display each clock cycle currently being accessed using the symbols described in
the following table.
SWn Normal Wait Cycles
PWn Page Wait Cycles
ASn Set-up Time from SHWT Address Validation to CE Fall
CSn Set-up Time from SHWT CE Fall to OE/SWE Fall
AHn Hold Time from SHWT CE Rise to Address Change
CHn Hold Time from SHWT OE/SWE Rise to CE Rise
ESn Synch Cycles of the External Input Signal
ACEn Address Clock Enable Cycles
Sn Other Cycles
(5) Shaded areas ( ) in the diagrams are undefined values.