User's Manual

FLC-BTM501 Datasheet
Flaircomm Microelectronics Confidential
-13-
4. Physical Interfaces
4.1 Power Supply
The transient response of the regulator is important. If the power rails of the module are supplied
from an external voltage source, the transient response of any regulator used should be 20μs or less.
It is essential that the power rail recovers quickly.
4.2 Reset
The module may be reset from several sources: RESETB pin, power-on reset, a UART break
character or via a software configured watchdog timer.
The RESETB pin is an active low reset and is internally filtered using the internal low frequency
clock oscillator. A reset will be performed between 1.5 and 4.0ms following RESETB being active.
It is recommended that RESETB be applied for a period greater than 5ms.
At reset the digital I/O pins are set to inputs for bi-directional pins and outputs are tri-state. The PIOs
have weak pull-ups.
Pin Name / Group
Pin Status on Reset
USB_DP
Input with PD
USB_DN
Input with PD
UART_RX
Input with PD
UART_TX
Tri-state output with PU
SPI_MOSI
Input with PD
SPI_CLK
Input with PD
SPI_CSB
Input with PU
SPI_MISO
Tri-state output with PD
RESETB
Input with PU
PIOs
Bi-directional with PU
AIOs
Output, drive low
RF-IN
High impedance
Table 4: Pin Status on Reset
Note: Pull-up (PU) and pull-down (PD) default to weak values unless specified otherwise.