at42qt1481 ATMEL Corporation, at42qt1481 Datasheet - Page 23

• Manufacturer Part Number: at42qt1481
• Description: 48-key Qmatrix Ic
• Manufacturer: ATMEL Corporation

Figure 3-2.
3.4
9621B–AT42–06/11
(Data from Host)
(Data from QT)
(from Host)
(from Host)
(from QT)
/DRDY
MOSI
MISO
CLK
UART Communications
/SS
3-state
SPI Slave-only Mode Timing (Fosc = 16 MHz)
?
high via pullup-R
? 7 6 5 4 3 2 1 0
S2
7 6 5 4 3 2 1 0
Data shifts out of QT on falling edge
Data shifts in to QT on rising edge
S1
{Command byte}
Figure 3-1.
See also
UART mode is selected as soon as the QT1481 receives any data on the UART Rx pin. There is
no other configuration required to make the QT1481 operate in UART mode.
UART mode communications function in the same basic way as SPI communications. The baud
rate is adjusted by means of setup parameter SR
rate has been set, the QT1481 must be reset for the new rate to take effect.
The major difference with SPI mode is that the UART mode is asynchronous and so the host
does not clock the QT1481. No framing SS or clock signal is required, simplifying the interface
greatly. Return data is sent from the QT1481 back to the host when the data is ready.
Multidrop capability: Tx floats within 10 µs after each transmitted byte. This line can be shared
with other UART based peripherals. Tx includes an internal 20 k – 50 k pull-up resistor to
Vdd to prevent the line from floating down.
Section 5.17 on page
S3
Communications Signals – SPI
3-state
S1: >125 ns
S5: <100 µs
S4
S5
Host MCU
P_OUT
S2: <20 ns
S6
S6: >1 µs
MISO
MOSI
P_IN
SCK
? 7 6 5 4 3 2 1 0
48.
7 6 5 4 3 2 1 0
{optional 2nd command byte}
S3: >25 ns
S7: >125 ns
S7
S8
S4: <20 ns
S8: >125 ns
S9
(Section 5.17 on page
S9: >250 ns
QT1481
DRDY
SS
SCK
MISO
MOSI
{null byte or next command to get QT response}
? 7
7 6 5 4 3 2 1 0
AT42QT1481
6 5 4 3
48). Once a new baud
data response
2 1 0
23