z80189 ZiLOG Semiconductor, z80189 Datasheet - Page 102

• Manufacturer Part Number: z80189
• Description: Z80180, Z8s180, Z8l180 Mpu Operation
• Manufacturer: ZiLOG Semiconductor

Z8018x
Family MPU User Manual
87
Refresh cycles may be programmed to be either two or three clock cycles
in duration by programming the REFW (Refresh Wait) bit in the Refresh
Control Register (RCR). The external WAIT input and the internal Wait
State generator are not effective during refresh.
Figure 44 depicts the timing of a refresh cycle with a refresh wait (TRW)
cycle.
MCi
Refresh cycle
MCi+1
TR1
TRW* TR2
Refresh signal
(Internal signal)
Refresh address
A0 — A7
MREQ
RFSH
NOTE: * If three refresh cycles are specified, TRW is inserted.
Otherwise, TRW is not inserted
MC: Machine Cycle
Figure 44.
Refresh Cycle Timing Diagram
UM005003-0703