MCP2140 Microchip Technology, Inc., MCP2140 Datasheet - Page 15

• Manufacturer Part Number: MCP2140
• Description: The MCP2140 Embeds Irda Protocol Handling And Bit Encoding/decoding, And Provides The Lowest Cost, Lowest Power Consumption Solution For Adding Irda Connectivity to Embedded Systems
• Manufacturer: Microchip Technology, Inc.

2.10
The IR data rate of the MCP2140 is fixed at 9.6 kbaud.
The actual throughput will be less due to several fac-
tors. The most significant factors are under the control
of the developer. One factor beyond the control of the
designer is the overhead associated with the IrDA
standard. A throughput example is shown in
Figure 2-9 shows the CTS waveform, what the state of
the buffers can be and the operation of the Host UART
and IR interfaces.
Figure 2-10 shows the screen-capture of a Host Con-
troller transmitting 240 bytes. Data is not transmitted
after CTS goes high (so only a maximum of 23 bytes of
the 29 byte buffer are utilized). Between data packets,
the CTS time can vary, depending on the Primary
Device (see blue circled CTS pulse in Figure 2-10).
FIGURE 2-9:
FIGURE 2-10:
CTS
2003 Microchip Technology Inc.
Buffers and Throughput
Receive Buffer Empty
MCP2140 Can Receive Data Receive Buffer Has 22 Bytes,
HOST UART RECEIVE BUFFER AND CTS WAVEFORM
HOST CONTROLLER TRANSMISSION OF A 240 BYTE PACKET
Table
CTS Pin Driven High
2-4.
Preliminary
Receive Buffer
Full (29 Bytes)
TABLE 2-4:
Note 1: Measured from Figure 2-10.
Transferred
Note:
Bytes
240
240
(3)
2: Interpolated from Figure 2-10.
3: 10 bits transferred for each byte.
IrDA throughput is based on many factors
associated with characteristics of the Pri-
mary and Secondary devices. These char-
acteristics may cause your throughput to
be more or less than is shown in Table 2-4.
IR Data Packet Starts Transmission
23 (max)
CTS Low
THROUGHPUT
Bytes/
29
Receive Buffer Empty
MCP2140 Can Receive Data
IR Data Packet Transmitted
(1)
MCP2140
0.810133
Time (S)
0.6500
DS21790A-page 15
Baud Rate
Effective
2962
3692
(1)
(2)