AT42QT1110-AZ View Datasheet(PDF) - Atmel Corporation
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AT42QT1110-AZ Datasheet PDF : 50 Pages
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With CRC Enabled, a CRC byte is also required (Figure 4-6). This is calculated for the two transmitted bytes (that is,
the Set command and the data byte).
For example, for the sequence shown in Figure 4-5 (0x95 — 0x0C), the CRC Byte is 0x9F. As is the case with the
other command types, when the QT1110 is expecting a CRC byte from the host, it calculates that byte in advance
and returns the expected value to the host in the same transmission as the host sends the CRC byte.
The sent data is not applied to the memory location until the CRC byte has been received and verified.
Figure 4-6. Positive Recalibration Delay Set Instruction – CRC Enabled
Host (Sends on MOSI)
Device (Responds on MISO)
Command: 0x95
Response: 0x55 (“Idle” – Fresh Command)
Simultaneous
Transmission
“Set” Data: 0x0C
Response: 0x95 (Command Just Received)
Command CRC: 0x9F
Response: 0x9F (Expected CRC)
4.1.5.2 Get Instructions
Get instructions are instructions that read the data from a location in the QT1110 memory map.
Figure 4-7. Positive Recalibration Delay Get Instruction – CRC Disabled
Host (Sends on MOSI)
Device (Responds on MISO)
Command: 0xD5
Response: 0x55 (“Idle” – Fresh Command)
Simultaneous
Transmission
Null: 0x00
“Get” Data: 0x0C (Positive Recalibration Delay)
The host sends the appropriate Get command, followed by a Null byte. The QT1110 returns the contents of the
addressed memory location.
Figure 4-7 shows the exchange for a report on the positive recalibration delay (assuming that the data byte is 0x0C).
With CRC Enabled, this exchange takes 4 bytes, with a command CRC transmitted by the host and a report CRC
returned by the QT1110 (see Figure 4-8 on page 16).
AT42QT1110-MZ / AT42QT1110-AZ [DATASHEET]
15
9570J–AT42–05/2013
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