It was thus said that the Great Jim once stated: I have the IBM PCjr Technical Reference Manual here (at home). Here's the relevent data from it (only the more important stuff): INFRA-RED RECEIVER ... Functional Description ... During keyboard operation, the emitted light is modulated, transmitted, and received in the following sequence: 1. A key is pushed. 2. The data stream is sent using the infra-red emitting diodes 3. The receiver amplifies and processes the signal. 4. The demodulated signal is sent to the system board. The signal received consists of an infra-red-light transmission modulated at 40 kHz. Application Notes The Infra-Red Receiver Board can serve as a general-purpose infra-red-receiver, however, the demodulator timings are tailored to the needs of the system. Programming Considerations The serially-encoded word is software de-serialized by the 8088 processor on the system unit. The leading edge of the start bit will generate a non-maskable interrupt (NMI). Once the processor enters the NMI routine to handle the deserialization, the keyboard-data line is sampled and the processor waits to sample the trailing edge of the start bit. When the trailing edge of the start bit is sampled, the processor will wait for 310 uS and sample the first half of the first data bit. This delay causes the processor to sample in the nominal center of the first half of the first data bit. The processor then samples the keyboard data every half- bit cell-time. The sampling interval is 220 uS. The processor samples each half-bit-sample 5 times and will determine the logical level of the sample by majority rule. This enables the processor to discrimitate against transient glitches and to filter out noise. The 8088 processor ultilizes one 8255 PPI bit (PORT C BIT 6) and shares one 8253 timer channel (CHANNEL 1) to do the software de-serialization of the keyboard data. ... Infra-Red connector Specifications Pin Signal Input/Output A01 +12V input A02 Ground input A03 Ground-shield input A04 I.R. TEST FREQ. input B01 Ground input B02 +5V input B03 -I.R. TEST FRQ output B04 Ground input IBM PCjr CORDLESS KEYBOARD ... Power is sent to the keyboard and serially-encoded data received by the system unit through the optional cord. When connected, the cord's keyboard connector removes the battery power and the -CABLE CONNECT signal disables the infra-red-receiver circuit. The disabling of the circuit also allows other infrared devices to be used without interfering with the system. The data which is received through the IR link or by the cord, have the same format. ... Transmitter Serially encoded words are transmitted to the system unit using the Infra-Red Link or the cable link. Encoded words are sent to the system unit with odd parity. Both the Infra-Red Link and the cable link use biphase serial-encoding and each is a simplex link. The 80C48 microprocessor does the biphase serial encoding with a bit cell of 440 uS. A biphase logically-encoded 1 is transmitted as logical 1 for the first half of the bit cell time and as a logical 0 for the second half of the bit cell. A bitphase logically-encoded 0 is transmitted as a logical 0 for the first half of the bit cell time and as a logical 1 for the second half of the bit cell. Each logical 1 transmission for the Infra-Red Link consists of a 40 kHz carrier burst at a 50% duty cycle. First bit Start Bit Second bit Data Bit 0 (Least Significant Bit) Third bit Data Bit 1 ... Ninth bit Data bit 7 (Most Significant Bit) Tenth bit Parity Bit Eleventh bit Stop Bit Eleven stop bits are inserted after every scan-code transmission. This is to allow some processor bandwidth between keystrokes to honor other types of interrupts, such as serial and time-of-day. Cable: | biphase 1 | | biphase 0 | ----+ +---------- -----------+ +---------- | | | | +------+ +------+ | Bit cell | | Bit Cell | ->| 220uS|<- | | ->| 220uS|<- ->| 440 uS |<- ->| 440 uS |<- Infra-Red | biphase 1 | | biphase 1 | ----+WW+------------- -----------+WW+--------------------- |WW| 40 kHz |WW| 40 kHz +WW+ @ 50% duty cycle +WW+ @ 50% duty Cycle | | | ->|220uS |<- ->| |<-62.5uS | | ->| |<-| 62.5uS ->| 440uS |<- ->| 440uS | The scancodes the application program receives via INT 16h (or even from INT 09h) are compatible with the original IBM PC 83-key keyboard (to maintain compatibility). The NMI routine decodes the serial stream, then calls INT 48h with the scan code in AL to concert the 62-key code to the 83-key code, which it stores into port 60h, then calls INT 09h. Unfortunately, the tech ref is quite vague on what keys return which scan codes, so you may have to actually play with INT 48h to see the actual codes. The BIOS listing is less than clear 8-) -spc (I would recomend getting IBM Technical Reference Part #6322963)