FDC37M607 datasheet(115/182 Pages) SMSC

115 / 182 page

115

CPU-to-Host Communication

The FDC37M60x CPU can write to the Output

Data

via

A write

to this register automatically sets Bit 0 (OBF) in

the Status register. See Table 49.

Table 49 - Host Interface Flags

8042 INSTRUCTION

FLAG

OUT DBB

Set OBF, and, if enabled, the KIRQ output signal goes high

Host-to-CPU Communication

The host system can send both commands and

data to the Input Data register.

The CPU

differentiates between commands and data by

reading the value of Bit 3 of the Status register.

When bit 3 is "1", the CPU interprets the register

contents as a command. When bit 3 is "0", the

CPU interprets the register contents as data.

During a host write operation, bit 3 is set to "1" if

SA2 = 1 or reset to "0" if SA2 = 0.

KIRQ

If "EN FLAGS" has been executed and P24 is

set to a one: the OBF flag is gated onto KIRQ.

The KIRQ signal can be connected to system

interrupt to

signify that the FDC37M60x CPU

has written to the output data register via "OUT

DBB,A". If P24 is set to a zero, KIRQ is forced

low. On power-up, after a valid RST pulse has

been delivered to the device, KIRQ is reset to 0.

KIRQ will normally reflects the status of writes

"DBB". (KIRQ is normally selected as IRQ1 for

keyboard support.)

If "EN FLAGS” has not been executed:

KIRQ

can be controlled by writing to P24. Writing a

zero to P24 forces KIRQ low; a high forces

KIRQ high.

MIRQ

If "EN FLAGS" has been executed and P25 is

set to a one:; IBF is inverted and gated onto

MIRQ. The MIRQ signal can be connected to

system interrupt to signify that the FDC37M60x

CPU has read the DBB register.

If "EN FLAGS” has not been executed, MIRQ is

controlled by P25,

Writing a zero to P25 forces

MIRQ low, a high forces MIRQ high. (MIRQ is

normally selected as IRQ12 for mouse support.)

Gate A20

A general purpose P21 is used as a software

controlled Gate A20 or user defined output.

EXTERNAL

KEYBOARD

AND

MOUSE

INTERFACE

Industry-standard PC-AT-compatible keyboards

employ a two-wire, bidirectional TTL interface

for data transmission.

Several sources also

supply PS/2 mouse products that employ the

same type of interface.

To facilitate system

expansion, the FDC37M60x provides four signal

pins that may be used to implement this

interface directly for an external keyboard and

mouse.

FDC37M607 Datasheet(PDF) 115 Page - SMSC Corporation

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