mcs7781 MosChip, mcs7781 Datasheet - Page 5

• Manufacturer Part Number: mcs7781
• Description: Usb To Irda Port
• Manufacturer: MosChip

Rev.
Functional Description
The MCS7781 consists of two major functional
blocks, the USB Controller and the Digital IR
Transceiver. The USB Controller provides Control,
Bulk-In, and Bulk-Out endpoints to the USB host.
The Digital IR Transceiver consists of transmit and
receive interfaces that connect to an analog IR front
end.
This USB/lrDA Bridge Controller has full interface
capability to connect between a USB bus, and an
IrDA compatible infrared transceiver device.
USB Interface
The USB Device Controller implements the USB
protocol engine.
single interface. Two Bulk end-points, with maximum
packet size of 64 Bytes, are used for data transfers.
The MCS7781 uses a vendor specific implementation
of IR configuration and control. Two vendor specific
requests are defined for this purpose, 1. Write Word,
and 2. Read Word. The vendor specific requests are
piped through the control endpoint.
“Write Word” is a 2 phase transaction which can
be used to write a single 16-bit register. The setup
phase of this command supplies both the index and
data value to be written into the register. There is no
data phase in this transfer.
“Read Word” requests are used to read the register
contents of MCS7781. It allows reading one 16-bit
register at a time. The setup phase specifies the
register address to be read, and the data is returned
in data phase.
2.1
It has one configuration with a
Digital IR Transceiver
The Digital IR Transceiver is responsible for driving
the transmit diode and receiving the digital input from
an analog IR front end. The primary components are
the transmit modulator, the receive demodulator, the
FIFO, the analog transmit section, and the register
array.
By programming the registers in the register array,
the device’s operation is determined.
registers are used to specify operations such as the
modulation scheme, the BAUD Rate, the current
frame size in the FIFO, the RX input selection, etc.
In steady state transmit operation, the USB controller
is filling the FIFO with data while the Digital IR
Transceiver is emptying it via the transmit modulator.
In steady state receive operation, the USB controller
is emptying the FIFO while the RX demodulator is
filling the FIFO.
IR FRAMING
Framing involves adding wrappers around the
payload received from NDIS to make a valid IR
frame. MCS7781 uses a custom framing style to
achieve low gate counts. The hardware and software
together play a role in making SIR, MIR, and FIR
frames.
MCS7781
USB to IrDA Port
Various
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