R01UH0136EJ0210 Rev.2.10
Page 147 of 800
Jul 31, 2012
M16C/64A Group
11. Bus
11.3.5.6
RDY
Signal
This signal is provided for accessing external devices which need to be accessed at low speed. If
input to the
RDY
pin is low at the last falling edge of BCLK in the bus cycle, one wait state is inserted
in the bus cycle. While in 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 input to the
RDY
pin is detected high at the falling edge of BCLK, the remaining bus cycle
is executed. Figure 11.4 shows Examples in Which Wait State Was Inserted into Read Cycle by
RDY
Signal. To use the
RDY
signal, set the corresponding bit (among bits CS3W to CS0W) in the CSR
register to 0 (with wait state). When not using the
RDY
signal, pull-up the
RDY
pin.
Figure 11.4
Examples in Which Wait State Was Inserted into Read Cycle by
RDY
Signal
11.3.5.7
BCLK Output
When the PM07 bit in the PM0 register is set to 0 (output enabled), a clock with the same frequency
as the CPU clock is output as BCLK from the BCLK pin. Refer to 8.4 “CPU Clock and Peripheral
Function Clocks”.
BCLK
RD
CSi
(i = 0 to 3)
RDY
tsu(RDY - BCLK)
BCLK
RD
CSi
(i = 0 to 3)
RDY
tsu(RDY - BCLK)
Separate bus
Multiplexed bus
Accept timing of RDY signal
Accept timing of RDY signal
tsu(RDY - BCLK)
: Wait using software
: Wait using RDY signal
: Duration for RDY input setup
The above diagrams assume bits CSEi1W to CSEi0W (i = 0 to 3) in the CSE register are 00b (one wait).
Summary of Contents for M16C/60 Series
Page 853: ...M16C 64A Group R01UH0136EJ0210...