upd70f3017ay Renesas Electronics Corporation., upd70f3017ay Datasheet - Page 94

• Manufacturer Part Number: upd70f3017ay
• Description: V850/sa1tm 32-/16-bit Single-chip Microcontroller
• Manufacturer: Renesas Electronics Corporation.

4.5.2 External wait function
inserted in a bus cycle by sampling the external wait pin (WAIT) to synchronize with the external device.
and on-chip peripheral I/O areas, similar to programmable wait.
clock in the T2 and TW states of the bus cycle. If the setup/hold time at sampling timing is not satisfied, the wait state
may or may not be inserted in the next state.
4.5.3 Relationship between programmable wait and external wait
programmable wait and the wait cycle controlled by the WAIT pin. In other words, the number of wait cycles is
determined by whichever side has the greatest number.
below, three wait states will be inserted in the bus cycle.
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When an extremely slow device, I/O, or asynchronous system is connected, any number of wait states can be
The external wait signal is data wait only, and does not affect the access times of the internal ROM, internal RAM,
Input of the external WAIT signal can be done asynchronously to CLKOUT and is sampled at the falling edge of the
A wait cycle is inserted as a result of an OR operation between the wait cycle specified by the set value of
For example, if the number of programmable waits and the timing of the WAIT pin input signal are as illustrated
Remark
: Valid sampling timing
Programmable wait
Wait by WAIT pin
Programmable wait
Wait by WAIT pin
Wait control
WAIT pin
CLKOUT
Figure 4-6. Example of Inserting Wait States
CHAPTER 4 BUS CONTROL FUNCTION
T1
Figure 4-5. Wait Control
User’s Manual U12768EJ4V1UD
T2
TW
TW
TW
Wait control
T3