W77C32 Datasheet, PDF (40/78 Pages) Winbond – 8 BIT MICROCONTROLLER

W77C32/W77C032A
Last Cycle
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Instruction
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Machine Cycle
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Machine Cycle
MOVX instruction cycle
C1 C2 C3 C4 C1 C2 C3 C4 C1 C2 C3 C4 C1 C2 C3 C4 C1 C2 C3 C4 C1 C2 C3 C4
CLK
ALE
PSEN
WR
PORT 0
A0-A7
D0-D7 A0-A7
D0-D7 A0-A7
D0-D7
A0-A7
D0-D7
PORT 2
MOVX Inst.
Address
Next Inst.
Address
MOVX Data
Address
MOVX Inst.
Next Inst.
Read
A15-A8
A15-A8
MOVX Data out
A15-A8
A15-A8
Figure 10: Dada Memory Write with Stretch Value = 2
8.4 Wait State Control Signal
Either with the software using stretch value to change the required machine cycle of MOVX instruction,
the W77C032 provides another hardware signal WAIT to implement the wider duration of external
data access timing. This wait state control signal is the alternate function of P4.0 such that it can only
be invoked to 44-pin PLCC/QFP package type. The wait state control signal can be enabled by setting
WS (ROMMAP.7) bit. When enabled, the setting of stretch value decides the minimum length of MOVX
instruction cycle and the device will sample the WAIT pin at each C3 state before the rising edge of
read/write strobe signal during MOVX instruction. Once this signal being recongnized, one more
machine cycle (wait state cycle) will be inserted into next cycle. The inserted wait state cycles are
unlimited, so the MOVX instruction cycle will end in which the wait state control signal is deactivated.
Using wait state control signal allows a dynamically access timimg to a selected external peripheral.
The WS bit is accessed by the Timed Access Protection procedure.
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