LM8300 datasheet(12/20 Pages) NSC

12 / 20 page

9.0 Functional Description (Continued)

lines. This option can be used in high noise environments to

significantly improve performance and accuracy of the touch

screen controller.

The default setting is filter path enabled.

$A2: Toggle disable/enable self-power down

Reply Byte #1: $CA (Acknowledge)

Byte #2: (0 = now disabled, 1 = now enabled)

This command can switch between self-power down mode

enable or disabled. Refer to the Power Save Mode section

for details. The default setting is Self-Power Down mode

enabled. If the echo mode is enabled, any command byte

send to the device will be echo back and executed.

$A3: Toggle disable/enable echo mode

Reply Byte #1: $CA (Acknowledge)

Byte #2: (0 = now disabled, 1 = now enabled)

The echo mode is available for debugging purposes. If en-

abled, the touch screen controller will echo back any data

that is received via the UART interface.

The default setting is Echo mode disabled.

$A4: Toggle disable/enable pressure measurement

Reply Byte #1: $CA (Acknowledge)

Byte #2: (0 = now disabled, 1 = now enabled)

The pressure measurement sets the touch screen to also

sample the Z-axis when reading the X and Y coordinates.

The default setting is pressure measurement enabled.

$A5: Toggle disable/enable calibration checking.

Reply Byte #1: $CA (Acknowledge)

Byte #2: (0 = now disabled, 1 = now enabled)

If the cablibration checking is enabled, the cablibration map-

ping must be the values shown in ??? to ???.

$A7: Wakeup

There is no reply byte to this command.

When the self-power down mode of the device is enabled,

the touch screen driver must send a wakeup command prior

to any command byte(s). If the self-power down mode of the

TSC is enabled. The wakeup command must also to be sent

if the driver puts the TSC in power-down mode via the

shutdown command.

$A8: Shutdown

Reply Byte #1: $CA (Acknowledge)

When the TSC driver wants the controller to go into power

save mode it sends a shutdown command to the controller.

The driver needs to send a wakeup to the controller before

starting up the communication again.

With the TSC has the self-power-down mode enabled, then

a touchdown on the touch screen will wake-up the TSC from

shutdown mode in addition to sending the wake up com-

mand. If the self-power-down mode is disabled, then only the

wakeup command can wake-up the controller from shut-

down mode (i.e. wake-up on touchdown is disabled).

$AF: Soft reset (restart the controller)

Reply Byte #1: $CA (Acknowledge)

Byte #2: $CB/$CC (Self test OK/Self test fail)

When the PC driver sends the soft reset command, the

touch screen controller executes a soft reset, which clears

and re-initializes all internal RAM configuration registers

from on-chip FLASH and performs a self-check of internal

RAM and program memory.

CONTROLLER REPLIES

$CF: Timeout.

Communication timeout has occurred, and current command

has been aborted.

$CE: Re-send

Request the TSC driver to resend the last command. This

command is used if the controller does not understand the

received command or a buffer overrun condition occurs.

$CC: Self test fail (done at startup, reset, and after

calibration)

$CB: Self test OK (done at startup, reset, and after

calibration)

$CA: Acknowledge

$C4: Calibration coordinates OK

This is sent if the coordinates are within the predefined

value.

$C8: Error / TX Buffer overrun

This is added to the last place in transmit buffer to signal that

a buffer overrun has occurred.

$C7: Software Version number

Byte #2: First byte of version number

Byte #3: Second byte of version number

Byte #4: Third byte of version number

$80: Format tablet for Z-axis disabled (see Format Table

section for more info.)

Byte #2: Status, low X and low Y

Byte #3: High X

Byte #4: High Y

$90: Format tablet for Z-axis enabled (see Format Table

section for more info.)

Byte #2: Status, low X and low Y

Byte #3: High X

Byte #4: High Y

Byte #5: Z-axis (0-127)

10.0 Oscillator

OSC_IN is the clock input while OSC_OUT is the clock

generator output to the crystal. Table 1. Crystal Oscillator

Configuration,

A = 25˚C, VCC =5V shows the component values required

for various standard crystal values. Figure 2 shows the

crystal oscillator connection diagram.

20037215

FIGURE 2. Crystal Oscillator

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