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POWER-UP |
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The IR101 device begins it power-up sequencing and autoconfiguration as soon as power is supplied. The BD and MD inputs are sampled and the output mode is set up accordingly. The IR101 monitors IRIN and RXD to automatically configure the IRIN and TXD polarities, repectively. Power-up is complete within 700ms. |
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NORMAL OPERATION |
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The IR101 receives NP1 serial data strings and provides the command (key) codes to the host via a standard serial interface. In detail, once the serial string is received, it is sum-checked and decoded. If the device ID coded matches that of the IR101, the command code is output to the host. Only properly-formed, error-free strings will produce output from the IR101.
The IR101 will assert the LED output signaling that a valid IR string has been decoded. It will remain asserted for approximately 150ms after the end of the last properly decoded NP1 string. During repeat sequences the LED output will be asserted continuously as the NP1 protocol specifies a repeat period of 100ms, ±10ms, which is less than the LED assertion period. |
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OUTPUT FORMAT (MD is high) |
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Data from the IR101 is output as a single, binary byte reprenting the 8-bit command code received. Just like RS232 serial data, the byte is output LSb-first with one start bit, one stop bit and no parity. This mode is ideal for direct microcontroller interfacing. |
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OUTPUT FORMAT (MD is low) |
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Data from the IR101 is output as a 5-byte, 8-bit clean ASCII string. The string is comprised of a start byte "$", 2 ASCII/hex digits representing the command code and is terminated with a carriage return and linefeed (CRLF). For example, an IR command of "AB" would cause this string to be output: $AB<CR><LF>. Just like RS232 serial data, each byte is output LSb-first with one start bit, one stop bit and no parity. This mode is idea for environments where higher-level serial protocols are in place and binary data could be misinterpreted as control characters. |
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Configuration |
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IR101 configuration is set with three signals: BD, MD and RXD. BD and MD set the baud rate and output modes, repectively. The RXD input can either be connected to a host serial output to force automatic output polarity selection or forced high or low, specifically. Whatever level is sensed on RXD during power-up becomes the level associated with a logical 1 for both the RXD and TXD signals.
RXD is continuously sampled for conditions that indicate a change in signal polarity. If RXD is negated (set to logic 0 as in a start bit) for longer than 25ms, the polarity of both RXD and TXD are inverted. Anytime the previous circumstance is encountered the signal polarity will be adjusted. This function is inplace to allow for slow peripheral start-up and/or (re)configuration at run time. The polarity of the IRIN signal autoselects its polarity. This is done at power-up and during normal operation. If IRIN is asserted continuously for more than 25ms, an error is sensed and the polarity of IRIN is inverted. This reconfiguration will occur anytime the previous circumstance is encountered. This function is inplace to allow for slow peripheral start-up and/or (re)configuration at run time.
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Input
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Should the RXD signal be connected to a host serial output, the IR101 can receive commands that produce addtional output to the host. There are two possible commands. The first is "A" (0x41). It echos a "B" (0x42) back to the host. This command is useful in applications where higher-level protocols are in place and is used to determine the presense of the IR101.
The second command is "V" (0x56). This command echos a version string back to the host. The version string is comprised of a manufacturer identifier, a protocol identifer, a device version number and the system (or customer) ID code the IR101 is set to receive. For example: "IRS NP1 V1.1 ID=0101". This string is followed by a carriage return and linefeed.
Should these functions not be needed, RXD should be forced to the level that indicates a logical 1 for the TXD signal. |
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Electrical Characteristics |
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Absolute Maximum Ratings |
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Parameter
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Value |
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Temperature, Ambient
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-40°C to +125°C |
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Temperature, Storage
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-65°C to +150°C |
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Vdd (with respect to Vss)
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+7.0V
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Inputs (with respect to Vss)
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-0.6V to Vdd + 0.6V |
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Total Power Dissipation
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600mW
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Maximum Supply Current
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120mA |
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Input Clamp Current
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± 20mA |
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Output Clamp Current
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± 20mA |
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Maximum Output Current (sourced)
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20mA
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Maximum Output Curreint (sunk)
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20mA
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DC Characteristics |
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Charateristic
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Symbol
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Min
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Typ
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Max
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Unit |
Operating Temperature
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TOP
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-40
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25 |
85 |
°C |
Operating Voltage
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VDD |
2.5
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5 |
5.5 |
V |
Supply Current
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IDD |
- |
0.9 |
1.6 |
mA |
Input Low Voltage
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VIL |
- |
- |
0.15 * VDD
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V |
Input High Voltage
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VIH |
0.25 * VDD + 0.8
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- |
- |
V |
Input Leakage Current
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IIL |
- |
- |
± 5
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uA |
Output Low Voltage
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VOL |
- |
- |
0.6 |
V |
Output High Voltage
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VOH |
VDD - 0.7
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- |
- |
V |
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AC Characteristics
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Charateristic
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Symbol
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Min
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Typ
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Max
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Unit |
Initialization Time (from power applied) |
TINIT
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450 |
700 |
mS |
Serial Data Rate
BD = 1
BD = 0 |
DRATE
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9600
2400 |
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baud |
LED Assertion Period |
LEDON
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135 |
150 |
165 |
mS |
Input Polarity Error Timeout |
POLERR
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22.5 |
25 |
27.5 |
mS |
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Copyright © 2003 Infrared Remote Solutions, Inc. |
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