519
CHAPTER 22 EXTERNAL DEVICE EXPANSION FUNCTION
Figure 22-4. Instruction Fetch from External Memory
(a) No wait (PW1, PW0 = 0, 0) setting
(b) Wait (PW1, PW0 = 0, 1) setting
(c) External wait (PW1, PW0 = 1, 1) setting
ASTB
RD
Lower Address
Operation CodeAD0-AD7
A8-A15 Higher Address
WAIT
ASTB
RD
AD0-AD7
A8-A15
Lower Address
Operation Code
Higher Address
Internal Wait Signal
(1-clock wait)
ASTB
RD
AD0-AD7
A8-A15

Lower Address Operation Code

Higher Address