mcs7840 MosChip, mcs7840 Datasheet - Page 8

• Manufacturer Part Number: mcs7840
• Description: Usb-2.0 To Four Serial Ports
• Manufacturer: MosChip

Page 8
MCS7840
USB-2.0 to Four Serial Ports
UART Functional Description
Overview
The UARTs are high performance serial ports that comply with the 16c550 specifi cation. All UARTs are similar
in operation and function, and are described in this section. The function of a single UART is described below.
Operation Modes
The UARTs are backward compatible with 16c450 and 16c550 devices. The operation of the port depends
upon the mode settings, which are described throughout the rest of this section. The modes, conditions and
corresponding FIFO depth are tabulated below.
450 Mode
After the hardware reset, bit-0 of the FIFO Control
Register (FCR) is cleared, and the UART is
compatible with the 16c450 mode of operation.
The transmitter and receiver FIFOs (referred to as
the “Transmitter Holding Register” and “Receiver
Holding Register” respectively) have a depth of
one.
This mode of operation is known as “Byte Mode”.
UART Mode
450
550
FIFO Size
16
1
550 Mode
After the hardware reset, writing a 1 to FCR[0]
will increase the FIFO size to 16, providing
compatibility with 16c550 devices.
In 16c550 mode, the device has the following
features:
•
•
•
RTS/CTS hardware fl ow control or
DSR/DTR hardware fl ow control
Infrared IrDA format transmit & receive
mode
Deeper (16-Byte) FIFOs
FCR[0]
0
1
Rev.
1.2