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Pin 8 (UART_DCD) is active low. It is normally 3.3v. When a connection is live this pin is low. This
means that when this pin is converted to RS232 voltage levels it will have the correct voltage level for
assertion.
Pin 10 (UART_DSR) is an input, with active low logic. It should be connected to the DTR output of the
host. When the BISM2 Module is in high speed mode (See definition for S Register 507), this pin
should be asserted by the host to ensure that the connection is maintained. A deassertion is taken to
mean that the connection should be dropped, or an online command mode is being requested.
Pin 27 (VCC_3V3 monitor) may only be used for monitoring purposes. It must not be used as a
current source.
The GPIO pins can be accessed using S Registers 621 to 628. GPIO4 is connected to an LED on the
module. If these I/O pins are set for input, then the LED will be driven by the host and appropriate
drive current requirements must be satisfied. A Logic 1 switches on the LED.
GPIO3 is also used for DTR output (active low). See S Register 552 & 553.
Analogue 0 and 1 should not exceed 1.8v and S Registers 701 and 702 are used to access them.
3.3 Electrical Specifications
3.3.1 Absolute Maximum ratings
Absolute maximum ratings for supply voltage and voltages on digital and analogue pins of the Module
are listed below; exceeding these values will cause permanent damage.
Parameter Min Max Unit
Peak current of power supply 0 100 mA
Voltage at digital pins -0.3 3.7 V
Voltage at POWER pin 3.6 7 V
3.3.2 Recommended Operating Parameters
3.3.2.1 Power Supply
Signal Name Pin No I/O Voltage level Comments
Vcc 29 I 3.6V to 7.0V I
typ
= 30mA
GND 11, 15, 18,
30, 36, 38
6 Ground terminals to be attached
in parallel
VCC_3V3 27 O 3.3V typical For monitoring only. No current
source
3.3.2.2 RS-232 Interface
Signal Name Pin No I/O Signal level Comments
UART_TX 21 O
V
OL
max=0.2V
V
OH
min=2.8V
UART_RX 25 I
V
IL
max=0.8V
V
IH
min=2.1V
V
IH
max=3.7V
UART_CTS 19 I
V
IL
max=0.8V
V
IH
min=2.1V
V
IH
max=3.7V