Oki BISM2 manual Application Examples, RS232 Modem Signals

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9. Application Examples

9.1RS232 Modem Signals

Just as a telephony modem has control and status lines, the blu2i Module also provides for 6 control and status lines as per the table below. The direction column is as seen from the module’s viewpoint.

Direction	Function
IN or OUT *	CI also known as RI (Ring Indicate)
IN or OUT *	DCD (Data Carrier Detect)
IN	DSR (Data Set ready)
OUT	DTR (Data Terminal Ready)
IN	CTS (Clear to Send)
OUT	RTS (Request to Send)

* configurable with S register 552

The first four lines are under program control. These use four of the GPIO pins and are mapped to I/O as per the table below. The last two are under control of the UART driver and their functionality is always enabled.

Direction	Connector Pin Label	Function
IN/OUT	GPIO1	General Purpose I/O
IN/OUT	GPIO2	General Purpose I/O
IN/OUT	UART_RI	Input/Output from module
IN/OUT	UART_DCD	Input/Output from module
IN	UART_DSR	Input to Module
IN/OUT	GPIO3/UART_DTR	General Purpose I/O (or DTR functionality)
IN/OUT	GPIO4/LED	General Purpose I/O (LED)
IN/OUT	GPIO5	General Purpose I/O
IN/OUT	GPIO6	General Purpose I/O
IN/OUT	GPIO7	General Purpose I/O
IN/OUT	GPIO8	General Purpose I/O

Notes:

1.PIO4 (DSR) is used by the blu2i module to sense that the host is connected, and is intricately linked with connections. For outgoing calls, if this line is not asserted then an error is indicated. Similarly for AT+BTP and AT+BTG.

While in a call, for appropriate modes, a de-assertion means fall into command state. If the de- assertion exists for longer than the period specified in S Register 519 then the connection is dropped as if an ATH command was received.

2.PIO2 (RI), is normally de-asserted. When an incoming connection is detected it will be asserted, until the connection is either answered or rejected using ATA and ATH respectively. See S Registers 552 & 553 for more details