MCP2122-E/SNG Microchip Technology, MCP2122-E/SNG Datasheet - Page 7

• Manufacturer Part Number: MCP2122-E/SNG
• Description: Infrared Encoder/Decoder
• Manufacturer: Microchip Technology

2.4
The MCP2122 requires an external clock source to
operate. The 16XCLK pin is the device clock input (see
Figure 2-5) and is independent of the host UART
interface or the IR interface. The 16XCLK determines
all timing during device operation. It is the edge of the
16XCLK pin that causes activity to occur.
The 16XCLK signal can also be referred to as a bit
clock (BITCLK). There are 16 BITCLKs for each bit
time. The BITCLKs are used for the generation of the
Start bit, the eight data bits and the Stop bit.
When the embedded system could be receiving IR
communication, the MCP2122 is required to have the
16XCLK signal clocking at the expected frequency and
have minimal variation in frequency. Between data
bytes (Stop bit to Start bit), the 16XCLK frequency can
be changed. This may occur in systems where the host
controller is implementing one of the IrDA standard
application layer protocols (such as IrObex).
FIGURE 2-6:
FIGURE 2-7:
 2004 Microchip Technology Inc.
16XCLK
16XCLK
(output)
(output)
(input)
(input)
16XCLK (Bit Clock)
(input)
(input)
RXIR
TXIR
RX
TX
16XCLK AND RX/RXIR
16XCLK AND TX/TXIR
3 CLK
16 16XCLK
16 16XCLK
Bit A
Bit A
Preliminary
3 CLK ( ~ 4 s)
16 16XCLK
16 16XCLK
When the embedded system does not want to receive
IR communications, the 16XCLK clock can be disabled
(static). This will reduce the power consumption of the
system.
Figure 2-6 shows the relationship of the 16XCLK signal
to the RXIR input, which then determines the RX output
signal. Figure 2-7 shows the relationship of the
16XCLK signal to the TX input, which then determines
the TXIR output signal. For device timing information,
refer to
FIGURE 2-5:
Section 4.0 “Electrical
16XCLK
16 16XCLK
16 16XCLK
Bit B
Bit B
DEVICE CLOCK SOURCE
MCP2122
MCP2122
Characteristics”.
DS21894A-page 7