Communication ICs IrDA infrared communication IC (SIR compatible) RPM-801CB Series The RPM-801CB Series is an infrared communication IC that is compatible with the IrDA (1.0). The infrared LED, PIN photodiode and modulator / demodulator circuit have been combined on to a single package. LED current can be controlled using external resistor, and an internal register is provided for setting the baud rate and pulse width of the transmitted light. Connection to a UART requires just three lines (transmit, receive, and control) and a clock. Applications Cellular telephones, pagers, PDA, PHS, notebook PCs, and printers. Features 1) Low power consumption. 2) Infrared emitting, receiver, and modulator / demodulator on the chip. 3) Compatible with the IrDA (1.0). 4) Built-in powerdown mode. 5) Power supply voltage input range 2.7V to 5.5V. 6) External clock input. 7) Light emitting pulse width can be varied. Block diagram 631 Communication ICs FPin descriptions FAbsolute maximum ratings (Ta = 25_C) FRecommended operating conditions (Ta = 25_C) 632 RPM-801CB Series Communication ICs RPM-801CB Series Input / output circuits 633 Communication ICs FElectrical characteristics (unless otherwise noted, Ta = 25_C, VDD = 3V) 634 RPM-801CB Series Communication ICs RPM-801CB Series Circuit operation (1) IrDA format (2) Register function Control character format As shown in the Fig.2, the control character is made up of four address bits, four data bits, a start bit and a stop bit. (3) Explanation of the registers Register table 635 Communication ICs RPM-801CB Series 1) Control register 1 2) Control register 2 ECHO 0 No control character echo back ECHO 1 Control character echo back ECAN 0 Reception of transmitted (self emitted) data not cancelled ECAN 1 Reception of transmitted (self emitted) data cancelled RXEN 0 Receiver off RXEN 1 Receiver on TXEN 0 Transmitter off TXEN 1 Transmitter on LOAD 0 Do not load the clock divider register value LOAD 1 Load the clock divider register value ∗ The LOAD bit automatically becomes 0 after the * clock divider register value is loaded. 3) Clock divider register value 1 4) Clock divider register value 2 Baud rate = M input clock frequency / 8 M = (DIV4 select value) (DIV3,2 select value) (DIV1,0 select value) ∗ At reset, the value is set to 1 / 2. The reset baud rate is therefore: 1 / 2 input clock frequency / 8. 5) Output pulse width register 1 636 Communication ICs RPM-801CB Series 6) Output pulse width register 2 Output pulse width = N input clock period / 2 N = (PW4 value) (PW3,2 value) (PW1,0 value) Note) N x 4 / M M = (DIV4 multiplier) (DIV3,2 multiplier) (DIV1,0 multiplier) (4) Timing chart (1) Reset operation Fig.3 (2) Register write Fig.4 637 Communication ICs RPM-801CB Series (3) Echo back Fig.5 (4) Transmit Fig.6 (5) Receive Fig.7 (6) Echo cancel Fig.8 638 Communication ICs RPM-801CB Series (7) Power down Fig.9 ∗ T1 is 1 / baud rate. Application example Operation notes After the power is applied or after a reset via RESET, the baud rate generator is set to Clock / 16, so perform the control register setting operation at a communication rate of Clock / 16. To perform infrared communication after the power is applied or after a reset via RESET, first set the value 3 into control register 1 (both receiver and transmitter on). Determine the clock frequency according to the content of the clock divider registers 1 and 2. Set the pulse width in accordance with IrDA specifications. 639 Communication ICs Electrical characteristics curves External dimensions (Unit: mm) 640 RPM-801CB Series