W77L32 Datasheet, PDF (42/76 Pages) Winbond – 8-BIT MICROCONTROLLER

W77L32/W77L032A/W77M032A
Wait State Control Signal
Either with the software using stretch value to change the required machine cycle of MOVX instruction,
the W77L032 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.
Wait State Control Signal Timing ( when Stretch = 1 )
CLOCK
First
Machine
Cycle
Second
Machine
Cycle
Third
Machine
Cycle
MOVX Instruction
W ait-State
Cycle
C1 C2 C3 C4 C1 C2 C3 C4 C1 C2 C3 C4 C1 C2 C3 C4 C1 C2 C3 C4
ALE
PSEN
ADDRESS
RD / WR
WAIT
original rising edge
Extended duration
sample
W AIT
sample WAIT
Wait State Control Signal Timing ( when Stretch = 2 )
CLOCK
First
Machine
Cycle
Second
Machine
Cycle
Third
Machine
Cycle
Fourth
Machine
Cycle
MOVX Instruction
W ait-State
Cycle
C1 C2 C3 C4 C1 C2 C3 C4 C1 C2 C3 C4 C1 C2 C3 C4 C1 C2 C3 C4 C1 C2
ALE
PSEN
ADDRESS
RD / WR
WAIT
original rising edge
Extended duration
sample
W AIT
sample WAIT
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