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2-4
I/O Signal Descriptions
WRITEn - Intel Mode
The external host asserts WRITEn to start a write cycle.
READn must be HIGH during a write cycle, and CSn
must be LOW during a write cycle. The address is
registered on the falling edge of WRITEn. The data is
latched by the L64105 on the rising edge of WRITEn.
READ/READn Read/Write Strobe - Read Indicator
READ - Motorola Mode
The Motorola host asserts READ HIGH for a read cycle
and deasserts it for a write cycle. CSn must be asserted
to select the L64105.
Input
READn - Intel Mode
The Intel host asserts READn and holds WRITEn
deasserted to perform a read cycle. The address is
registered on the falling edge of READn. CSn must be
asserted to select the L64105.
DTACKn/RDYn
Data Acknowledge/Data Ready
DTACKn - Motorola Mode
The L64105 asserts this signal to indicate to the external
host that the current bus transaction (read or write) can
be completed. DTACKn is 3-stated if CSn is not asserted.
The bus cycle is terminated if the L64105 deasserts
DTACKn before the cycle is completed.
3-State Output
RDYn - Intel Mode
The L64105 asserts this signal to indicate to the external
host that the current bus transaction (read or write) can
be completed. RDYn is 3-stated if CSn is not asserted.
The bus cycle is terminated if the L64105 deasserts
RDYn before the cycle is completed.
WAITn
Wait
This signal may be used instead of DTACKn/RDYn by
hosts that require an inverted sense. The L64105 asserts
WAITn to indicate that its Host Interface is busy with a
read or write bus cycle and it deasserts it when the
current cycle is completed. WAITn is 3-stated when CSn
is not active.
3-State Output
INTRn
Interrupt
INTRn is an active-LOW, open-drain, output signal. The
L64105 asserts this signal to alert the host that an
OD Output