MCP2122 Microchip Technology, MCP2122 Datasheet - Page 5

• Manufacturer Part Number: MCP2122
• Description: Converts serial data from UART bitstreams to IrDA standard bitstreams (encodes) and from IrDA standard bitstreams to UART bitstreams ...
• Manufacturer: Microchip Technology

2.0
The MCP2122 is a low-cost infrared encoder/decoder.
The baud rate is the same for the host UART and IR
interfaces and is determined by the frequency of the
16XCLK signal, with a maximum baud rate of
115.2 Kbaud.
The MCP2122 is made up of these functional modules:
• Clock Driver (16XCLK)
• Reset
• IR Encoder/Decoder
The 16XCLK circuit allows a clock input to provide the
device clock.
The Reset circuit supports an external reset signal.
The IR Encoder logic takes a data bit and converts it to
the IrDA standard signal according to the IrDA standard
Physical Layer specification, while the IR Decoder
logic takes the IrDA standard signal and converts it to
8-bit data bytes.
2.1
As the device is powered up, there will be a voltage
range in which the device will not operate properly. The
device should be reset once it has entered the normal
operating range (from an out-of-voltage condition). The
RESET pin may then be forced high.
Other device operating parameters (such as frequency,
temperature, etc.) must also be within their operating
ranges when the device exits reset. Otherwise, the
device may not function as desired.
2.2
The MCP2122 is forced into the known state (RESET)
when the RESET pin is in the low state. Once the
RESET pin is brought to a high state, the device begins
normal operation (if the device operating parameters
are met). Table 2-1 shows the states of the output pins
while the device is in reset (RESET = Low). Table 2-2
shows the state of the output pins once the device exits
reset, RESET = L H (device in Normal Operation
mode).
The MCP2122 has a RESET noise filter in the RESET
input signal path. The filter will detect and ignore small
pulses.
Using the RESET pin to enter a low-power state is
discussed in
 2004 Microchip Technology Inc.
- IrDA Standard Encoder
- IrDA Standard Decoder
DEVICE OPERATION
Power-up
Device Reset
Section 2.9 “Minimizing
Power”.
Preliminary
TABLE 2-1:
TABLE 2-2:
2.3
It is highly recommended that the MCP2122 have a
decoupling capacitor (C
recommended as a starting value, but an evaluation of
the best value for your circuit/layout should be
performed. Place this decoupling capacitor (C
close to the MCP2122 as possible (see Figure 2-1).
FIGURE 2-1:
TX
RXIR
RESET
Name State
Name
Input Pin
Input Pin
capacitor)
(bypass
C
BYP
Decoupling
State
H
H
L
L
L
V
DD
H L
Output Pin
RX
—
—
H
DEFAULT OUTPUT PIN
STATES IN DEVICE RESET
DEFAULT OUTPUT PIN
STATES AFTER DEVICE
RESET (RESET = L H)
Output Pin
RX
State
H
V
V
RESET
16XCLK
TX
RX
DD
SS
State
DEVICE DECOUPLING
TXIR
L H
MCP2122
—
—
TXIR
L
BYP
L
L
). A 0.01 µF capacitor is
After 7 - 8 16XCLK
pulses, the TXIR pin
will pulse high.
After 4 16XCLK pulses,
RX = L.
MCP2122
Device in Reset mode
TXIR
RXIR
Comments
Comments
DS21894B-page 5
BYP
) as