ZBA Inc. BT44-291S ユーザーズマニュアル

 

BT44-291S

 

Page 13 of 18 

 

BlueCore4-External 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. 

The power on reset occurs when the VDD_CORE supply falls below typically 1.5V and is 

released when VDD_CORE rises above typically 1.6V. 

At reset the digital I/O pins are set to inputs for bi-directional pins and outputs are tri-stated. 

The PIOs have weak pull-downs. 

Following a reset, BlueCore4-External assumes the maximum XTAL_IN frequency, which 

ensures that the internal clocks run at a safe (low) frequency until BlueCore4-External is 
configured for the actual XTAL_IN frequency. If no clock is present at XTAL_IN, the oscillator in 
BlueCore4-External free runs, again at a safe frequency. 
 

11.1 

Pin States on Reset 

Table 11.15 shows the pin states of BlueCore4-External on reset. 

PIO[11:0] 

Input with weak pull-down 

UART_TX 

Output tri-stated with weak pull-up 

UART_RX 

Input with weak pull-down 

UART_RTS  Output tri-stated with weak pull-up 

UART_CTS  Input with weak pull-down 

SPI_CSB 

Input with weak pull-up 

SPI_CLK 

Input with weak pull-down 

SPI_MOSI 

Input with weak pull-down 

SPI_MISO 

Output tri-stated with weak pull-down 

AIO[1:0] Output, 

driving 

low 

RESETB 

Input with weak pull-up