Electronics America 8-Bit Single-Chip Microcontrollers User's Manual

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CHAPTER 22 EXTERNAL DEVICE EXPANSION FUNCTION
Figure 22-7. External Memory Read Modify Write Timing
(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
WR
Higher Address
AD0-AD7
A8-A15
WAIT
Hi-Z
Lower Address
Write DataRead Data
Lower Address
Higher Address
Internal Wait Signal
(1-clock wait)
Hi-Z
ASTB
RD
WR
AD0-AD7
A8-A15
Write DataRead Data
ASTB
RD
WR
AD0-AD7
A8-A15
Lower Address Write Data
Higher Address
Hi-Z
Read Data