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Expansion Bay Signal Definitions

The signals on the expansion bay connector are of two types: expansion bay control signals and ATA signals. Table 4-2 describes the control signals and Table 4-3 describes the ATA signals.

Table 4-2 Control signals on the expansion bay connector

Signal name	Signal description
/DEVID(0-2)	These signals identify the type of device in the expansion-bay module. A value of 011b identifies an IDE device; a value of 111b indicates no device is present.
/DEVIN	This signal should be low whenever a device is installed in the expansion bay; it is used by the KeyLargo IC to determine when a device has been inserted or removed. The expansion bay module should connect this pin to ground.
/IDE_RST	Reset signal.

Table 4-3 ATA signals on the expansion bay connector

Signal name	Signal description
/CS1FX	Register select signal. It is asserted low to select the main task file registers. The task file registers indicate the command, the sector address, and the sector count.
/CS3FX	Register select signal. It is asserted low to select the additional control and status registers on the IDE drive.
/DIOR	I/O data read strobe.
/DIOW	I/O data write strobe.
DMARQ	DMA request signal.
/DMACK	DMA acknowledge signal.
IDE_ADDR(0-2)	IDE device address; used by the computer to select one of the registers in the drive. For more information, see the descriptions of the /CS1FX and /CS3FX signals.
IDE_D(0-15)	IDE data bus, buffered from IOD(16-31) of the controller IC. IDE_D(0-15) are used to transfer 16-bit data to and from the drive buffer. IDE_D(0-7) are used to transfer data to and from the drive's internal registers, with IDE_D(8-15) driven high when writing.
IOCHRDY	I/O channel ready; when driven low by the IDE drive, signals the CPU to insert wait states into the I/O read or write cycles.
IDE_INTRQ	IDE interrupt request. This active high signal is used to inform the computer that a data transfer is requested or that a command has terminated.
/IDE_RST	Hardware reset to the IDE drive.

Note

Signal names that begin with a slash (/) are active low.