LM8500HVA9 National Semiconductor, LM8500HVA9 Datasheet - Page 12

• Manufacturer Part Number: LM8500HVA9
• Description: IC TOUCHSCREEN CONTROLLER 44PLCC
• Manufacturer: National Semiconductor
• Type: Resistiver

Specifications of LM8500HVA9

• Touch Panel Interface: 4-Wire
• Number Of Inputs/keys: 1 TSC
• Resolution (bits): 10 b
• Data Interface: UART
• Data Rate/sampling Rate (sps, Bps): 38.4k
• Voltage - Supply: 2.7 V ~ 5.5 V
• Current - Supply: 11.5mA
• Operating Temperature: 0°C ~ 70°C
• Mounting Type: Surface Mount
• Package / Case: 44-PLCC
• Voltage Supply Source: Single Supply
• For Use With: LM8500-REF-01 - BOARD EVALUATION LM8500
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant
• Sampling Rate (per Second): -
• Other names: *LM8500HVA9

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9.0 Functional Description
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
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
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
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.
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
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)
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.
Reply Byte #1: $CA (Acknowledge)
Byte #2: (0 = now disabled, 1 = now enabled)
Reply Byte #1: $CA (Acknowledge)
Byte #2: (0 = now disabled, 1 = now enabled)
Reply Byte #1: $CA (Acknowledge)
Byte #2: (0 = now disabled, 1 = now enabled)
Reply Byte #1: $CA (Acknowledge)
Byte #2: (0 = now disabled, 1 = now enabled)
Reply Byte #1: $CA (Acknowledge)
Reply Byte #1: $CA (Acknowledge)
Byte #2: $CB/$CC (Self test OK/Self test fail)
(Continued)
12
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
$CB: Self test OK (done at startup, reset, and after
$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
$80: Format tablet for Z-axis disabled (see Format Table
$90: Format tablet for Z-axis enabled (see Format Table
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,
T
for various standard crystal values. Figure 2 shows the
crystal oscillator connection diagram.
A
= 25˚C, V
section for more info.)
Byte #2: Status, low X and low Y
Byte #3: High X
Byte #4: High Y
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)
Byte #2: First byte of version number
Byte #3: Second byte of version number
Byte #4: Third byte of version number
calibration)
calibration)
CC
FIGURE 2. Crystal Oscillator
= 5V shows the component values required
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