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Z8018x
Family MPU User Manual
27
CPU Internal Operation
Bus Release Cycle CPU Cycle
T1
T1
T1
T1
TX
TX
TX
T1
Phi
–
A0
A19
–
D0
D7
MREQ
IORQ
RD, WR
BUSREQ
BUSACK
Figure 17.
Bus Exchange Timing During CPU Internal Operation
Wait State Generator
To ease interfacing with slow memory and I/O devices, the Z8X180 uses
Wait States (TW) to extend bus cycle timing. A Wait State(s) is inserted
based on the combined (logical OR) state of the external WAIT input and
an internal programmable wait state (TW) generator. Wait States (TW)
can be inserted in both CPU execution and DMA transfer cycles.
When the external WAIT input is asserted Low, Wait State(s) (TW) are
inserted between T2 and T3 to extend the bus cycle duration. The WAIT
input is sampled at the falling edge of the system clock in T2 or TW. If the
WAIT input is asserted Low at the falling edge of the system clock in TW,
another TW is inserted into the bus cycle.
Note:
WAIT input transitions must meet specified setup and hold
times. This specification can easily be accomplished by
UM005004-0918
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Questions and answers
are there a timing diagrams for PUSH and POP instructions?
The timing diagrams for the PUSH and POP instructions for the ZiLOG Z8018 Series are as follows:
POP Instruction (e.g., POP IX or POP IY):
- Machine Cycle 1 (MC1): Fetch POP opcode.
- Machine Cycle 2 (MC2): Fetch address code.
- Machine Cycle 3 (MC3): Read from memory at SP (Stack Pointer); data goes to low byte (e.g., IXL or IYL).
- Machine Cycle 4 (MC4): Read from memory at SP+1; data goes to high byte (e.g., IXH or IYH).
PUSH Instruction (e.g., PUSH IX or PUSH IY):
- Machine Cycle 1 (MC1): Fetch PUSH opcode.
- Machine Cycle 2 (MC2): Fetch address code.
- Machine Cycle 3 (MC3): Decrement SP by 1 and write high byte (e.g., IXH or IYH) to memory at SP.
- Machine Cycle 4 (MC4): Decrement SP by 1 and write low byte (e.g., IXL or IYL) to memory at SP.
Each machine cycle includes three T-states (T1, T2, T3), and memory control signals (such as MREQ, RD, WR) are active as needed during these cycles.
This answer is automatically generated