QT1100A-ISG View Datasheet(PDF) - Quantum Research Group
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QT1100A-ISG Datasheet PDF : 42 Pages
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Without the EEPROM the QT1100A will operate in a default
mode, designed to accommodate most touch sensing
requirements (Section 2.12, below).
Serial Mode Setups: The two serial interfaces permit a
host MCU to program control setups into the QT1100A on
power-up or even during normal operation, allowing low cost
reconfigurability. This is performed with a block of data,
referred to as a Setups block.
The Setups block must end with a CRC check byte. If the
optional 93LC46A EEPROM is also used, the Setups block
will be stored locally so that there is no need to reload after
each power-up.
2.12 Standalone Operation, No EEPROM
The device can operate in Standalone Mode without serial
communications or EEPROM using only its parallel scanport
interface. (See Table 1.3, page 6 and Figure 1.3, page11)
There are some minor differences in the default settings and
behaviour in Standalone Mode without EEPROM compared
with other modes:
1. K2L is enabled on all keys*
2. SYNC is enabled (SE = 1)*
3. No serial comms - CRDY is always clamped low
*These exceptions are noted in Table 4-1, page 31.
2.13 EEPROM Functionality
The serial EEPROM is used to store Setups information
which alters the device behavior. If the EEPROM is not used,
the device uses default parameters to operate , or,
customized parameters loaded into the device via serial
interface.
The EEPROM’s functionality is not necessary when used
with a serial interface. The host serial controller can send the
Setups to the QT1100A following each power-up. In a serial
mode, the EEPROM eliminates the need to send Setups
after each power-up since they are stored locally.
The EEPROM must contain the value 0xD6 as its first byte
or it will not be read. The table on page 31 shows the
contents required for this EEPROM. A CRC must be
appended to the end of the EEPROM table, or, the CRC can
be replaced by a 0xD6 code, in which case no CRC
checking will be performed (not recommended except as a
development shortcut). A blank EEPROM will be
programmed properly when the host sends a Setups block to
the device.
EEPROM corruption is automatically detected every 2
seconds during normal run operation . If the EEPROM is
found to be corrupt or erased, the EEPROM error flag is set
in the device status byte (command 0xC2); the EEPROM
itself is not corrected. If the device is using serial
communications, the host controller should reload the
Setups and then reset the device.
If in a serial mode an EEPROM is not installed, pin DIEE
should be connected to Vdd.
2.14 Scanport Interface
The scanport functions as a ‘legacy replacement’ for a matrix
scanned XY keyboard. Single inputs (one-of-three) on
Scan_In lines result in a pattern of bits on Scan_out pins
depending on the keys that are active. If no keys are active
the Scan_out pins remain inactive. See connection pinlists,
Tables 1.1 and 1.2.
All logic on the scanport is ‘active high’ for both Scan_In and
Scan_Out. The scanport maps to the Scan_In and Scan_Out
pins as per Table 2.1.
Table 2.1 - Scanport I/O Mapping
Scan In 0
Scan In 1
Scan In 2
Scan Out
0
Key 0
Key 4
Key 8
Scan Out
1
Key 1
Key 5
Key 9
Scan Out
2
Key 2
Key 6
0
Scan Out
3
Key 3
Key 7
0
The scanport is enabled if the CMODE pin is strapped low .
The UART is also enabled in this mode but it can be ignored ;
if UART serial is not used, TX should be connected to Vss.
Scanport Latency: The latency of the scanport from
Scan_In to Scan_Out is 120µs maximum. UART transfers do
not affect this response time . Scanning software has to take
this delay into account, i.e. it should not expect the
Scan_Out pins to be stable until 120µ s after setting the
Scan_In pins.
One easy way to use the scanport is to read the scanport
before changing the Scan_In signals. Normally, Scan_In
should be changed to a new state every 1 ~ 2ms. Faster
scanning than this will not result in a perceptibly faster
response time. Therefore, if the Scan_Out lines are read
immediately before changing the Scan_In signals, the host
controller will not have to wait for the 120µs scanport
latency.
System Response Time: The setting of the two detection
integrators (see Section 4.9) strongly affects the basic
device response time. The host’s scan rate adds to this time.
If the basic QT1100A response time is set to 80ms, and the
host completely scans the device every 50ms, the total
response time can be a very slow 130ms.
One way to maintain good response time while minimizing
host activity is to have the host monitor the LED/STAT pin,
perhaps via interrupt, and service the scanport only when the
LED/STAT pin becomes active. (See Section 4.8, page 27)
Sleep/Wake Function: Sleep/Wake can only be used in
conjunction with a serial mode which sets the sleep state via
a command, and so Sleep is not possible in Scanport mode
without a serial interface.
Sync Mode with Scanport: Sync mode can be enabled
using an EEPROM having the correct Setups; Sync mode
also works in standalone mode without an EEPROM (see
also Section 4.12). In Sync mode the acquire bursts are
synchronized to the external clock source; the scanport will
operate correctly while the device is waiting for a sync edge.
2.15 Start-up Sequencing
After power-up or reset the flag ‘Reset Occurred ’ will be set.
The user can read this flag with command 0xC2. This flag
can be reset by issuing a ‘0xC2 0xC7’ command sequence.
If an EEPROM is installed and the EEPROM’s CRC does not
match its contents, or the first byte is not 0xD6, the error flag
“EEPROM Error” will be set. In this case, the default Setup
settings will be used but the EEPROM contents will stay
unchanged.
2.16 Error Detection and Reporting
A ‘major error’ is one where an enabled key signal falls
below LBLL (Section 4.13) or rises above a value of 4095, or
where there is a CRC error in RAM or EEPROM Setups. The
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Copyright © 2003-2005 QRG Ltd
QT1100A-ISG R3.02/1105
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