cs5535 National Semiconductor Corporation, cs5535 Datasheet - Page 110

• Manufacturer Part Number: cs5535
• Description: Geode Cs5535 Companion Multi-function South Bridge
• Manufacturer: National Semiconductor Corporation

www.national.com
4.9
The Keyboard Emulation Logic (KEL) provides a virtual
8042 keyboard controller interface that is used to map non-
legacy keyboard and mouse sources to this traditional
interface. For example, Universal Serial Bus (USB) sources
are “connected” to this interface via System Management
Mode (SMM) software. It also allows mixed environments
with one LPC legacy device and multiple new (USB)
devices. It produces IRQ and ASMI outputs.
Features
• Provides a virtual 8042 keyboard controller interface.
• Allows mixed environments.
KEYBOARD EMULATION LOGIC
14 MHz
14 MHz
1 kHz
Local Bus Data
to
IN
32
*
*
*
*
*
OUT
Local Bus Clock
USB1_SOF
LPC_IRQ12
USB2_SOF
32
LPC_IRQ1
Reset
Control
Control
Output
KEL X
Status
1 kHz Clock
Input
HCE
HCE
HCE
HCE
Figure 4-21. KEL Block Diagram
* Read-Back Multiplexer is not shown
Logic (KEL)
Keyboard
Emulator
110
• Produces IRQ and ASMI outputs.
• Employs a clock control logic for power management
• No USB controller required for KEL to operate.
4.9.1
The Keyboard Emulation Logic (KEL) with Port A is illus-
trated in Figure 4-21. Strictly speaking, these are separate
functions. However, since they both effect the FA20#
(Force processor Address bit 20 to zero when low), the two
functions are implemented together. The Keyboard Emula-
tion Logic is the most complex and is discussed first.
purposes.
Keyboard Emulation and Port A
Port 064h Write
Port 060h and
Port A Write
Port 060h
Port 064h
& Read
Read
Read
IRQ 1 (to PIC Subsystem)
IRQ 12 (to PIC Subsystem)
EmulationInterrupt
ASMI
EmulationEnable
SnoopEnable
FA20#
INIT Keyboard
A20 Keyboard
INIT Port A
A20 Port A
Port A Enable
Local Bus Data
OUT
*
*
8
IN
Revision 0.8
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