IRM7001 Vishay, IRM7001 Datasheet - Page 3

• Manufacturer Part Number: IRM7001
• Description: Sir Modulator/demodulator
• Manufacturer: Vishay

Document Number: 82576
Revision 17-August-01
Table 2. Pin Out and Signal Description
Function
The IRM7001 can be used in conjunction with a microcontrol-
ler/microprocessor that has a serial communication interface
(UART). Prior to communication the processor selects the
transmission baudrate by selecting appropriate levels on the
A0-A2 lines. This process sets up the communication system
to operate at the prescribed data rate. After this initial step,
serial data can be transmitted or received at the prescribed
data rate.
The IRM7001 consists of two state machines–the SIR Encode
and SIR Decode blocks, and a sequential block Clock Divide,
which synthesizes the required internal signal INT-CLOCK,
based on the inputs A0-A2 and the CLK_ SEL line. The
IRM7001 can be placed into Internal Clock Mode (CLK_SEL
set to low) or External Clock Mode (CLK_ SEL set to high).
The internal clock signal INT_CLOCK source is then gated
appropriately through to the INT_CLOCK signal. In application
where the external 16XCLK signal is provided, there is no need
to provide an oscillator.
Signal
16X CLK
TXD
RCV
A0-A2
CLK_SEL
GND
NRST
IR_RCV
IR_TXD
PULSEMOD
POWER-DN
OSCOUT
OSCIN
V
CC
Pin
1
2
3
4-6
7
8
9
10
11
12
13
14
15
16
Type
DIGIN
DIGIN
DIGOUT
DIGIN
DIGIN
DIGIN
DIGIN
DIGOUT
DIGIN (with
pulldown)
DIGIN (with
pulldown)
ANAOUT
ANAIN
Description
Positive edge triggered input clock signal that is set to 16 times the data transmission baudrate. This
clock is used to drive the Encoder/Decoder state machine. Depending on the application, the
16XCLK can be provided by the application circuitry, or the internal clock divider circuitry can be
used. Selection of operating mode (Internal or External clock) is selected by the CLK_SEL line. If
External clock mode is selected, the application circuitry need not provide an oscillator.
Negative edge triggered input signal that is normally tied to the SOUT signal of a UART (serial data
to be transmitted). Data is modulated and output as IR_TXD.
Output signal normally tied to SIN signal of a UART (received serial data). RCV is the demodulated
output of IR_RCV.
Clock multiplex signals. These signals are asserted to select the appropriate clock rate to support
the following baudrate: 115200, 57600, 38400, 19200, 9600, 4800 and 2400 bps.
Active high signal, used to activate either the Internal or External clock. A high on this line activates
the External clock (16XCLK), or if it is pulled low, the Internal clock is used.
Chip ground
Active low signal used to reset the IrDA-SIR Decode state machine. Normally this line is tied to the
POR (power on reset) line of the circuit or simply to Vcc. In addition to resetting the circuitry, this
signal can be asserted to disable any data reception.
Input is from the SIR optoelectronics. Input signal is a 3/16th pulse which is demodulated (pulse
stretched) to generate the RCV (3) output signal.
This signal is the modulated TXD signal.
A level high on this input puts the chip into the monoshot transmit mode. In this mode, when there
is a negative transition on the TXD input, a rising edge on the internal transmit modulation state ma-
chine will activate a high pulse on IR_TXD for 6 crystal clock cycles. With a 3.6864MHz crystal, this
corresponds to 1.63us. This mode cannot be used in conjunction with the 16XCLK clock. It is meant
to be used with the external crystal clock. By default, this input pin is pulled to GND.
A high on this input puts the internal oscillator in POWERDOWN MODE. The internal oscillator nor-
mally is not powered down.
Crystal Oscillator input
Crystal Oscillator input
Power (see Electrical Specifications for detail)
The SIR Encode block is driven by TXD (negative edge trig-
gered signal), which initiates the modulation state machine,
resulting in the modulated IR_TXD signal (which drives the SIR
compatible electronics).
The SIR Decode block is driven by the IR_RCV signal (nega-
tive edge triggered signal, derived from the optoelectronics).
IR_RCV is demodulated by the SIR Decode block resulting in
the RCV signal, which represents the stretched input pulse.
In addition, there is a pin provided to the user, called the
PULSEMOD. A high level input on this pin activates the 1.6us
mode on the IR_TXD. In this mode, whenever there is a nega-
tive edge on the TXD, the rising edge on the modulation state
machine will set the IR_TXD signal high for 6 crystal clock
cycles no matter what the selection on A2, A1 and A0 lines is.
With a crystal frequency of 3.6864MHz, this corresponds to a
high pulse of 1.63us.
www.vishay.com
3