HD6435348R Hitachi Semiconductor, HD6435348R Datasheet - Page 152

• Manufacturer Part Number: HD6435348R
• Description: Single-Chip Microcomputer
• Manufacturer: Hitachi Semiconductor

7.3.3 Pin Auto-Wait Mode
The pin auto-wait mode is selected when WMS1 = 1 and WMS0 = 1.
In this mode the WAIT function of the P1
In this mode, the number of wait states indicated by bits WC1 and WC0 are inserted, but only if
there is a Low input at the WAIT pin.
Figure 7-4 shows the timing of this operation when the wait count is 1.
In the pin auto-wait mode, the WAIT pin is sampled only once, on the falling edge of the ø clock
in the T
wait states indicated by bits WC1 and WC0. The WAIT pin is not sampled during the Tw and T
states, so no additional wait states are inserted even if the WAIT pin continues to be held Low.
This mode offers a simple way to interface a low-speed device: the wait states can be inserted by
routing a decoded address signal to the WAIT pin.
ø
WAIT
A
RD, AS,
DS (Read)
D –D
WR, DS
(Write)
D –D
19
7
7
2
–A
state. If the WAIT pin is Low at this time, the wait-state controller inserts the number of
* The arrowheads indicate the times at which the WAIT pin is sampled.
0
0
0
T
1
External address
Write data
Figure 7-4 Pin Auto-Wait Mode
T
2
*
Read data
4
T
/WAIT pin is used automatically.
3
133
Fig. 7-4
T
1
T
2
*
External address
Write data
T
W
Read data
T
3
3