CS5535 datasheet(112/555 Pages) NSC

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KEL Functional Description (Continued)

ms counter can be used (MSR 5140001Fh[3:2]). At the

beginning of each frame, the conditions that define asyn-

chronous EEs are checked and, if an EE condition exists,

the EE is signaled to the host. This has the effect of reduc-

ing the number of EEs that are generated for legacy input

to no more than 1,000 per second. The number of emula-

tion interrupts is limited because the maximum rate of data

delivery to an application cannot be more than 1,000 bytes

per second. A benefit of this rule is that, for normal key-

board and mouse operations, only one EE is required for

each data byte sent to the application. Additionally, delay of

the EE until the next Start of Frame causes data persis-

tence for keyboard input data that is equivalent to that pro-

vided by an 8042.

4.9.6

Theory - KEL EEs

There are three EEs that produce the signal KEL ASMI.

These three EEs are: Character Pending, Input Full, and

External IRQ. An A20 sequence is a possible Input Full EE.

The A20Sequence bit in the HCE_Control register (KEL

Memory Offset 100h[5]) will be set in this case. The signal

KEL ASMI is an active high pulse one Local bus clock in

width and sent to the Diverse Integration Logic (DIVIL).

This signal is only asserted when the EmulationEnable bit

in HCE_Control is high (KEL Memory Offset 100h[0] = 1),

that is, emulation is enabled. For an EE, KEL also option-

ally produces an Emulation IRQ (KEL_EMU_IRQ). This

signal is a level and is only asserted when the EE Routing

(EER) bit in MSR_KELX_CTL (MSR 5140001Fh[1]) is low.

De-asserting KEL_EMU_IRQ requires clearing the appro-

priate bit in the HCE_Control or KEL HCE_Status registers

(KEL Memory Offset 100h and 10Ch).

For

the

keyboard

A20Sequence,

KEL

sets

the

KEL_A20_ASMI_FLAG if enabled in the DIVIL.

Keyboard INIT and A20 are generated as appropriate when

emulation

enabled

snoop

enabled

MSR_KELX_CTL. KEL ASMI is generated as appropriate

when emulation is enabled. KEL ASMI is not generated

when emulation is disabled and snoop is enabled.

Key-

board A20 under snoop does not require service beyond

the DIVIL GLD_MSR_SMI (MSR 51400002h); that is, KEL

does not need to be manipulated. The InputFull bit in

HCE_Status (KEL Memory Offset 10Ch[1]) will set, but

does

not

require

service.

Each

new

keyboard

A20Sequence

will

set

the

KEL_INIT_ASMI_FLAG

enabled.

If a write to Port A changes the value of bit 1, the KEL sets

the PORTA_A20_ASMI_FLAG if enabled in the DIVIL. If bit

Port

written

KEL

sets

the

PORTA_INIT_ASMI_FLAG if enabled in the DIVIL. It also

sets Port A to the value 2; that is, only bit 1 is high. The

A20State bit in HCE_Control (KEL Memory Offset 100h[8])

is not effected.

The rate of application software reading of I/O Address

060h is dependent on the alternate device interrupt rate or

SOFEVENT (Start of Frame Event, MSR 5140001Fh[3:2])

when the CharacterPending bit is used in the HCE_Control

EE per application software read of I/O Address 060h when

CharacterPending is set.

The rate of application software writing of I/O Addresses

060h and 064h is no greater than SOFEVENT. Generally,

there is one KEL EE per application write to I/O Address

060h.

SOFEVENT is used to emulate normal delays associated

with a real 8042 controller and PS/2 device. Its source is

established via MSR 5140001Fh[3:2]. Its value is 1 ms

frame interval.

4.9.7

Theory - Mixed Environment

A mixed environment is one in which an alternate device

and a PS/2 device are supported simultaneously (e.g., a

USB keyboard and a PS/2 mouse). The mixed environment

is supported by allowing the emulation software to control

the PS/2 interface. Control of this interface includes captur-

ing I/O accesses to I/O Addresses 060h and 064h and also

includes capture of interrupts from the PS/2 keyboard con-

troller off the LPC. IRQ1 and IRQ12 from the LPC keyboard

controller are routed through the KEL. When External-

IRQEn in HCE_Control (KEL Memory Offset 100h[4]) is

set, IRQ1 and IRQ12 from the legacy keyboard controller

are blocked at the KEL and an ASMI is generated instead.

This allows the emulation software to capture data coming

from the legacy controller and presents it to the application

through the emulated interface. The behavior of IRQ1 and

IRQ12 with respect to ExternalIRQEn and IRQEN bits is

summarized in Table 4-16.

Table 4-16. KEL Mixed Environment

Emulation

Enable

ExternalIRQEn

IRQEN

LPC_IRQ1

LPC_IRQ12

OutputFull

Aux

IRQ1

Active

IRQ12

Active

Action

001

IRQ1

000

IRQ12

010

100

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