MCP2140-I/SO Microchip Technology, MCP2140-I/SO Datasheet - Page 19

• Manufacturer Part Number: MCP2140-I/SO
• Description: IC IRDA CONTROLLR DTE/DCE 18SOIC
• Manufacturer: Microchip Technology

Specifications of MCP2140-I/SO

• Package / Case: 18-SOIC (7.5mm Width)
• Controller Type: IRDA Standard Protocol Stack Controller
• Interface: UART
• Voltage - Supply: 3 V ~ 5.5 V
• Current - Supply: 2.2mA
• Operating Temperature: -40°C ~ 125°C
• Mounting Type: Surface Mount
• Maximum Operating Temperature: + 85 C
• Minimum Operating Temperature: - 40 C
• Mounting Style: SMD/SMT
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• For Use With: MCP2140DM-TMPSNS - BOARD DEMO FOR MCP2140
• Lead Free Status / Rohs Status: Lead free / RoHS Compliant

2.14.2
Discovery mode allows the Primary device to deter-
mine the capabilities of the MCP2140 (Secondary
device). Discovery mode is entered once the MCP2140
(Secondary device) has sent a XID response to the Pri-
mary device and the Primary device has completed
sending the XIDs and a Broadcast ID. If this sequence
is not completed, a Primary and Secondary device can
stay in NDM indefinitely.
When the Primary device has something to do, it
initiates Discovery, which has two parts. They are:
• Link initialization
• Resource determination
The first step is for the Primary and Secondary devices
to determine, and then adjust to, each other’s hardware
capabilities. These capabilities are parameters like:
• Data rate
• Turnaround time
• Number of packets without a response
• How long to wait before disconnecting
Both the Primary and Secondary devices begin com-
munications at 9600 baud, the default baud rate. The
Primary device sends its parameters and the Second-
ary device responds with its parameters. For example,
if the Primary device supports all data rates up to
115.2 kbaud and the Secondary device only supports
9.6 kbaud, the link will be established at 9.6 kbaud.
Once the hardware parameters are established, the
Primary device must determine if the Secondary device
has the resources it requires. If the Primary device has
a job to print, it must know if it’s talking to a printer, and
not a modem or other device. This determination is
made using the Information Access Service (IAS). The
job of the Secondary device is to respond to IAS que-
ries made by the Primary device. The Primary device
must ask a series of questions like:
• What is the name of your service?
• What is the address of this service?
• What are the capabilities of this device?
When all the Primary device’s questions are answered,
the Primary device can access the service provided by
the Secondary device.
During Discovery mode, the MCP2140 handles all
responses to the Primary device (see
without any communication with the Host Controller.
The Host Controller is inhibited by the CTS signal of the
MCP2140 from sending data to the MCP2140.
2003 Microchip Technology Inc.
Note:
The MCP2140 is limited to a data rate of
9.6 kbaud.
DISCOVERY MODE
Figure
2-13)
Preliminary
2.14.3
Once discovery has been completed, the Primary
device and MCP2140 (Secondary device) can freely
exchange data.
The MCP2140 uses a hardware handshake to stop the
local serial port from sending data when the MCP2140
Host UART Receiving buffer is full..
Both the Primary device and the MCP2140 (Secondary
device) check to make sure that data packets are
received by the other without errors. Even when data is
not required to be sent, the Primary and Secondary
devices will still exchange packets to ensure that the
connection hasn’t, unexpectedly, been dropped. When
the Primary device has finished, it transmits the “close
link” command to the MCP2140 (Secondary device).
The MCP2140 will confirm the “close link” command
and both the Primary device and the MCP2140 (Sec-
ondary device) will revert to the NDM state.
It is the responsibility of the Host Controller program to
understand the meaning of the data received and how
the program should respond to it. It’s just as if the data
were being received by the Host Controller from a
UART.
2.14.3.1
The MCP2140 identifies itself to the Primary device as
a modem.
However, the MCP2140 is not a modem, and the non-
data circuits are not handled in a modem fashion.
Note:
Note:
Note:
Data loss will result if this hardware
handshake is not observed.
If the NCM mode is unexpectedly termi-
nated for any reason (including the Primary
device not issuing a close link command),
the MCP2140 will revert to the NDM state
approximately 10 seconds after the last
frame has been received.
The MCP2140 identifies itself as a modem
to ensure that it is identified as a serial
device with a limited amount of memory.
NORMAL CONNECT MODE (NCM)
Primary Device Notification
MCP2140
DS21790A-page 19