DSP 104-plus, Reference Manual

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24 158004.B00
The polarity of the incoming signal on the IRRX pin is of opposite polarity to that on
the IRTX pin. The IRTX pin is normally low, and will emit a series of narrow positive
going pulses as a character is transmitted. These positive pulses are designed to
switch on the LED of the IrDA transmitter. For proper operation the IRRX receiver
must deliver to the Super I/O chip a signal that is normally high, but which pulses low
on receipt of a pulse of light from an IrDA transmitter. Depending on the nature of
your IrDA transceiver, this requirement may involve adding a logic inverter between
the IrDA transceiver and the IRRX pin on the TP400.
An IrDA optical transceiver is present on the top edge of the TCDEVPLUS. See the
TCDEVPLUS Technical Reference Manual for details of how to enable this.
The TCDEV Development system has no IrDA optical transceiver. However, the IrDA
pins are accessible on the TCDEV at jumper area E1 - the transmit signal on E1 pin
10 and the receive signal on E1 pin 7. By setting E1 jumpers to 7 - 8 and 9 - 10, and
removing other jumpers, the IrDA signals as well as power are available on the
mouse connector J8.
The Sharp-IR mode is fixed at 38.4k baud.
The Consumer-IR mode supports all the protocols currently used in remote-controlled
home entertainment equipment: RC-5, RC-6, RECS80, NEC and RCA.
For further information on the IrDA standards, see this web site:
www.irda.org
3.5 PRINTER PORT
The TP400 implements a full-function Centronics compatible printer port. This port is
the MS-DOS PRN device. The printer port is contained within the PC97317 Super I/O
chip.
The printer port features an 8-bit data port and the full compliment of control signals -
four output signals and five input signals.
The 8-bit data port is normally used as an output port for driving a printer. Provided
that the printer port is set up for bi-directional operation (which it is by default), then it
can also be used as an input port. The default setting (after reset) is output. To
configure the printer as an input bit 5 of the printer port Control Register must be set
to 1. To re-configure as an output set bit 5 to 0. The Control Register is a read/write
register located at address 37AH.
The printer port signals are brought out on the 50-way J4 I/O connector on the
TP400. On the TCDEVPLUS the parallel port is accessed via a PC compatible 25
way female D-type connector.
If enabled by software, the parallel port is able to use interrupt IRQ7 to interrupt the
processor. Users should note that the BIOS does not make use of interrupts for
accessing the printer port, but other software drivers may do so. See section 4.5 for a
discussion of interrupt allocation on the TP400.