CYW20734
Table 6. XTAL Oscillator Characteristics
Parameter Symbol
Output frequency Foscout
–
Tstartup
Pdrv
Conditions
Minimum
Typical
Maximum
Unit
kHz
ppm
ms
–
–
–
32.768
–
–
Frequency tolerance
Start-up time
Crystal-dependent
–
100
–
–
500
–
XTAL drive level
For crystal selection
For crystal selection
For crystal selection
0.5
–
–
μW
kΩ
XTAL series resistance
XTAL shunt capacitance
Rseries
Cshunt
–
70
1.3
–
–
pF
1.7 GPIO Ports
The CYW20734 has 40 general-purpose I/Os (GPIOs) in a 90-pin package.All GPIOs support programmable pull-ups and are capable
of driving up to 8 mA at 3.3V or 4 mA at 1.8V, except P26, P27, P28, and P29, which are capable of driving up to 16 mA at 3.3V or
8 mA at 1.8V.
Port 0–Port 1, Port 8–Port 19, Port 21–Port 23, and Port 28–Port 38
All of these pins can be programmed as ADC inputs.
Port 26–Port 29
P[26:29] consist of four pins. All pins are capable of sinking up to 16 mA for LEDs. These pins also have the PWM function, which
can be used for LED dimming.
1.8 Keyboard Scanner
The keyboard scanner is designed to autonomously sample keys and store them into buffer registers without the need for the host
microcontroller to intervene. The scanner has the following features:
■ Ability to turn off its clock if no keys are pressed.
■ Sequential scanning of up to 160 keys in an 8 × 20 matrix.
■ Programmable number of columns from 1 to 20.
■ Programmable number of rows from 1 to 8.
■ 16-byte key-code buffer (can be augmented by firmware).
■ 128 kHz clock that allows scanning of full 160-key matrix in about 1.2 ms.
■ N-key rollover with selective 2-key lockout if ghost is detected.
■ Keys are buffered until host microcontroller has a chance to read it, or until overflow occurs.
■ Hardware debouncing and noise/glitch filtering.
■ Low-power consumption. Single-digit µA-level sleep current.
1.8.1 Theory of Operation
The key scan block is controlled by a state machine with the following states:
1.8.2 Idle
The state machine begins in the idle state. In this state, all column outputs are driven high. If any key is pressed, a transition occurs
on one of the row inputs. This transition causes the 128 kHz clock to be enabled (if it is not already enabled by another peripheral)
and the state machine to enter the scan state. Also in this state, an
8-bit row-hit register and an 8-bit key-index counter is reset to 0.
Document Number: 002-14874 Rev. *S
Page 12 of 51
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