mcs7780 MosChip, mcs7780 Datasheet - Page 5

• Manufacturer Part Number: mcs7780
• Description: Usb 1.1 To Irda Port
• Manufacturer: MosChip

Rev. 1.2
Functional Description
The MCS7780 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 a USB protocol
engine. It has one configuration with a single interface.
Two Bulk endpoints with maximum packet size of 64
Bytes are used for data transfers. The MCS7780 uses
Vendor Specific commands for IR configuration and
control. Two vendor specific requests (“Write Word”
& “Read Word”) are defined for this purpose. 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.
The “Read Word” request is used to read the register
contents of the MCS7780. 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
the data phase.
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. Various 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.
MCS7780 uses a custom framing style to achieve low
gate count. The hardware and software together play
a role in making of SIR, MIR, and FIR frames.
MCS7780
USB 1.1 to IrDA Port
Page 5