Legacy-Free Keyboard/Embedded Controller with SPI and LPC Docking Interface
Table 13.18 Keyboard Scan-In Register
N/A
HOST ADDRESS
8051 ADDRESS
0x7F04
(R)
VCC1
N/A
POWER
DEFAULT
BIT
D7
D6
D5
D4
D3
D2
D1
D0
-
-
-
-
-
-
-
-
HOST TYPE
8051 R/W
BIT NAME
R
R
R
R
R
R
R
R
Reflects the state of KSI [7:0]
The value of the KSI[x] pins can be read through this register.
The pin values are latched during the read.
13.6
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 LPC47N350 provides four pairs of signal pins that may be used to
implement this interface directly for an external keyboard and mouse.
The LPC47N350 has four high-drive, open-drain output (external pull-ups are required), bidirectional port
pins that can be used for external serial interfaces, such as ISA external keyboard and PS/2-type mouse
interfaces. They are KBCLK, KBDAT, EMCLK, EMDAT, IMCLK, IMDAT, PS2CLK and PS2DAT.
The following function is assumed to be in the PS/2 PORT logic: The serial clock lines, KBCLK, EMCLK,
IMCLK and PS2CLK, are cleared to a low by VCC2 POR. This is so that any power-on self-test
completion code transmitted from the serial keyboard will not be missed by the LPC47N350 due to
power-up timing mismatches.
SMSC LPC47N350
153
Revision 1.1 (01-14-03)
DATASHEET
SMSC [ SMSC CORPORATION ]
