XR21V1414IM48 EXAR [Exar Corporation], XR21V1414IM48 Datasheet - Page 17

• Manufacturer Part Number: XR21V1414IM48
• Description: 4-CH FULL-SPEED USB UART
• Manufacturer: EXAR [Exar Corporation]

REV. 1.0.0
This register enables the UART TX and RX. For proper functionality, the UART TX and RX must be enabled in
the following order:
UART_ENABLE[0]: Enable UART TX
•
•
UART_ENABLE[1]: Enable UART RX
•
•
UART_ENABLE[7:2]: Reserved
These bits are reserved and should remain ’0’.
These registers are used for programming the baud rate. The V1414 uses a 19-bit divisor and 16-bit mask
register. Using the internal 48MHz oscillator, the 19-bit divisor is calculated as follows:
For example, if the the baud rate is 115200bps, then
CLOCK_DIVISOR0[7:0]: Baud rate clock divisor bits [7:0]
CLOCK_DIVISOR1[7:0]: Baud rate clock divisor bits [15:8]
CLOCK_DIVISOR2[2:0]: Baud rate clock divisor bits [18:16]
CLOCK_DIVISOR2[7:3]: Reserved
These bits are reserved and should remain ’0’.
A look-up table is used for the value of the 16-bit TX Clock mask registers. The index of the look-up table is
calculated as follows:
For example, if the baud rate is 115200bps, then the index will be:
The values for some baud rates to program the TX_CLOCK_MASK registers are listed in
rates that are not listed, use the index to select TX_CLOCK_MASK register values from
The values for some baud rates to program the RX_CLOCK_MASK registers are listed in
rates that are not listed, use the same index calculated for the TX_CLOCK_MASK register to select
RX_CLOCK_MASK register values from
3.3
3.3.1
3.3.2
3.3.3
3.3.4
Logic 0 = UART TX disabled.
Logic 1 = UART TX enabled.
Logic 0 = UART RX disabled.
Logic 1 = UART RX enabled.
UART Register Descriptions
FIFO_ENABLE_CHx = 0x1
UART_ENABLE = 0x3
FIFO_ENABLE_CHx = 0x3
CLOCK_DIVISOR = Trunc ( 48000000 / Baud Rate )
CLOCK_DIVISOR = Trunc ( 48000000 / 115200 ) = Trunc (416.66667) = 416
index = Trunc ( ( ( 48000000 / Baud Rate ) - CLOCK_DIVISOR ) * 32)
index = Trunc ( ( ( 48000000 / 115200 ) - 416 ) * 32) = Trunc (21.3333) = 21
UART_ENABLE Register Description (Read/Write)
CLOCK_DIVISOR0, CLOCK_DIVISOR1, CLOCK_DIVISOR2 Register Description (Read/Write)
TX_CLOCK_MASK0, TX_CLOCK_MASK1 Register Description (Read/Write)
RX_CLOCK_MASK0, RX_CLOCK_MASK1 Register Description (Read/Write)
Table
// Enable TX FIFO
// Enable TX and RX of that channel
// Enable RX FIFO
8.
17
4-CH FULL-SPEED USB UART
Table
Table
Table
XR21V1414
8.
7. For baud
7. For baud