
Rev.2.10 Apr 14, 2006 page 49 of 378
REJ09B0124-0210
M16C/6N Group (M16C/6NK, M16C/6NM) 7. Bus
________
Figure 7.4 Example in which Wait State was Inserted into Read Cycle by RDY Signal
BCLK
RD
CSi
(i=0 to 3)
RDY
tsu(RDY - BCLK)
BCLK
RD
CSi
(i=0 to 3)
tsu(RDY - BCLK)
In an instance of separate bus
In an instance of multiplexed bus
Accept timing of RDY signal
: Wait using RDY signal
: Wait using software
Accept timing of RDY signal
tsu(RDY-BCLK): RDY input setup time
Shown above is the case where bits CSEi1W to CSEi0W (i = 0 to 3) in the CSE register are
00b (one wait state).
RDY
________
7.2.6 RDY Signal
This signal is provided for accessing external devices which need to be accessed at low speed. If input on
________
the RDY pin is asserted low at the last falling edge of BCLK of the bus cycle, one wait state is inserted in
________
the bus cycle. While in a wait state, the following signals retain the state in which they were when the RDY
signal was acknowledged.
_______ _______ _____ ________ ________ ______ ________ __________
A0 to A19, D0 to D15, CS0 to CS3, RD, WRL, WRH, WR, BHE, ALE, HLDA
________
Then, when the input on the RDY pin is detected high at the falling edge of BCLK, the remaining bus cycle
________
is executed. Figure 7.4 shows an Example in which Wait State was Inserted into Read Cycle by RDY
________
Signal. To use the RDY signal, set the corresponding bit (bits CS3W to CS0W) in the CSR register to 0
________ ________
(with wait state). When not using the RDY signal, the RDY pin must be pulled-up.
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