FDC37B770 SMSC [SMSC Corporation], FDC37B770 Datasheet - Page 122

• Manufacturer Part Number: FDC37B770
• Description: ENHANCED SUPER I/O CONTROLLER WITH WAKE UP FEATURES
• Manufacturer: SMSC [SMSC Corporation]

CPU-to-Host Communication
The FDC37B77x CPU can write to the Output
Data
Host-to-CPU Communication
The host system can send both commands and
data to the Input Data register.
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 FDC37B77x 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.
OUT DBB
register
8042 INSTRUCTION
via
register DBB.
Set OBF, and, if enabled, the KIRQ output signal goes high
Table 49 - Host Interface Flags
The CPU
A write
122
to this register automatically sets Bit 0 (OBF) in
the Status register. See Table 49.
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 FDC37B77x
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
INTERFACE
Industry-standard PC-AT-compatible keyboards
employ a two-wire, bidirectional TTL interface
for data transmission.
supply PS/2 mouse products that employ the
same type of interface.
expansion, the FDC37B77x provides four signal
pins that may be used to implement this
interface directly for an external keyboard and
mouse.
FLAG
KEYBOARD
Several sources also
To facilitate system
AND
MOUSE