z80189 ZiLOG Semiconductor, z80189 Datasheet - Page 35

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

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UM005003-0703
Z8018x
Family MPU User Manual
Figure 10.
Operand and Data Read/Write Timing
The instruction operand and data read/write timing differs from Op Code
fetch timing in two ways:
•
•
Instruction operands include immediate data, displacement, and extended
addresses, and contain the same timing as memory data reads.
During memory write cycles the MREQ signal goes active in the second
half of T1. At the end of T1, the data bus is driven with the write data.
At the start of T2, the WR signal is asserted Low enabling the memory.
MREQ and WR go inactive in the second half of T3 followed by
disabling of the write data on the data bus.
A0
D0
MREQ
WAIT
–
The M1 output is held inactive
The read cycle timing is relaxed by one-half clock cycle because data
is latched at the falling edge of T3
–
A19
Phi
RD
M1
D7
Op Code Fetch (with Wait State) Timing Diagram
T1
T2
TW
TW
Op Code
T3
T1
T2