Installation and Operation
©
2006 Microchip Technology Inc.
DS51571B-page 19
2.5.2.2
MCP2120 OPERATION
The MCP2120 (U1) implements an IrDA standard encoder/decoder. The baud rate is
determined by the device frequency and the state of the BAUD2:BAUD0 pins. The
MCP2120 also has a Software Baud Rate mode which controls the baud rate via the
Host Controller software.
The key signals for the MCP2120-to-microcontroller (Host UART) interface are shown
in Table 2-6. The key signals for the MCP2120-to-IR transceiver circuit are shown in
Table 2-7.
TABLE 2-6:
MCP2120 HOST UART INTERFACE PINS
TABLE 2-7:
MCP2120 IR INTERFACE PINS
In addition to the signals described in Table 2-6 and Table 2-7, the MCP2120 RESET
input is connected to the RESET output of the Host Controller. The EN input can be
either hard-wired or controlled by the Host Controller.
Pin
Name
Pin
Number
(PDIP)
Pin
Type
Buffer
Type
Description
TX
12
I
TTL
Asynchronous receive; from Host Controller UART
RX
11
O
—
Asynchronous transmit; to Host Controller UART
BAUD0
10
I
TTL
BAUD2:BAUD0 specifies the Baud rate of the
device, or if the device operates in Software Baud
Rate mode
BAUD1
9
I
TTL
BAUD3
8
I
TTL
MODE
7
I
TTL
Selects the device mode (Data/Command) for
Software Baud Rate operation
Legend:
TTL = TTL compatible input
ST = Schmitt Trigger input with CMOS levels
I = Input
O = Output
Pin Name
Pin
Number
(PDIP)
Pin
Type
Buffer
Type
Description
TXIR
6
O
—
Asynchronous transmit to IrDA
®
standard
transceiver
RXIR
5
I
ST
Asynchronous receive from an infrared transceiver
Legend:
A = Analog
P = Power
I = Input
O = Output
