MCP2140A データシートの表示（PDF） - Microchip Technology

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MCP2140A

IrDA® Standard Protocol Stack Controller With Fixed 9600 Baud Communication Rate

Microchip Technology 

MCP2140A

2.10 Buffers and Throughput

The IR data rate of the MCP2140A is fixed at

9.6 kbaud. The actual throughput will be less due to

several factors. Many 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.

Depending on the application, throughput may be an

issue in one or both directions.

2.10.1 THROUGHPUT

Throughput is dependant on the direction that the data

is streaming and the characteristics of the Primary

Device and Secondary Device. Streaming throughput

from the Secondary Device may be different with

different Primary Devices. Also streaming throughput

from the Secondary Device may be different than

streaming throughput to the Secondary Device, with

the same Primary Device. Throughput examples are

shown in Table 2-4. These examples are based on

actual observed data communications.

Note:

IrDA throughput is based on many factors

associated with characteristics of the

Primary and Secondary devices. These

characteristics may cause your through-

put to be more or less than is shown in

Table 2-4.

Figure 2-11 shows an example communications

sequence between a Primary Device and a Secondary

Device (MCP2140A). In this example after the “Primary

Device Sends Open Link Frame”, the time for the

Secondary Devices response is fixed by the operation

of the MCP2140A. After the “Primary Device Decodes

Secondary Device Response” the “Primary Device

Responds to Secondary Device”. Throughput may be

improved if the application program can be written so

that the Primary Device response as fast as possible.

Also when the “Secondary Device Sends Data”, the

frame should have the maximum number of data bytes.

Figure 2-12 shows the screen-capture of a Host

Controller (and MCP2140A) streaming (transmitting)

250 bytes to a Primary Device (PIC24 + IrDA Standard

Stack Library).

Figure 2-13 shows the screen-capture of a MCP2140A

(and Host Controller) receiving 250 streamed bytes

from a Primary Device (PIC24 + IrDA Standard Stack

Library).

Figure 2-14 shows a second screen-capture of a Host

Controller (and MCP2140A) streaming (transmitting)

250 bytes to a Primary Device (Notebook PC with IR

port).

TABLE 2-4: THROUGHPUT EXAMPLES - 250 BYTES (3)

Primary Device

Secondary

Device

PC (6)

MCP2140A (5)

PIC IrDA Standard Stack (4)

PIC IrDA Standard Stack (4)

PDA (HP iPAQ hx2495b)

MCP2140

MCP2140A (5)

MCP2140A (5)

MCP2140A (5)

Data

Streaming

Direction

S -> P

S -> P

S -> P

P -> S

S -> P

250 Byte

Transmit Time

(ms) (1)

354

650 (7)

337

549

332

Effective

Baud Rate (2)

Comment

7062

3692

7418

4553

7530

Figure 2-14

Note 7

Figure 2-12

Figure 2-13

Figure 2-15

Note 1:

2:

3:

4:

5:

6:

7:

Measured from Figure. (see comment)

Interpolated from Figure. (see comment)

10 bits transferred for each byte.

Using the PIC24 Explorer 16 Development Board with IR Transceiver Board

Using the MCP215X/40 Data Logger Demo Board and Board Firmware V1.4

IBM 600X Thinkpad (notebook computer) running Windows XP Professional (SP1)

MCP2140 Data Sheet, DS21790, Table 2-4, MCP2140 transmitted 240 bytes in this transmit time.

FIGURE 2-10:

HOST UART RECEIVE BUFFER AND CTS WAVEFORM

CTS

Receive Buffer

Full (60 Bytes)

IR Data Packet Transmitted

Receive Buffer Empty

Receive Buffer Empty

Receive Buffer Has 59 Bytes,

MCP2140A Can Receive Data

MCP2140A Can Receive Data CTS Pin Driven High

IR Data Packet Starts Transmission

DS22050A-page 16

© 2007 Microchip Technology Inc.

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