XR21V1412_10 Datasheet, PDF (15/30 Pages) Exar Corporation – 2-CH FULL-SPEED USB UART

XR21V1412
REV. 1.1.0
2-CH FULL-SPEED USB UART
3.0 REGISTER SET DESCRIPTION
The internal register set of the V1412 consists of 3 different blocks of registers: the UART Manager, UART
registers and UART miscellaneous registers. The UART Manager controls the TX and RX enables and FIFOs
of all UART channels. The UART registers configure and control the remaining UART channel functionality
with the exception of low latency mode, wide mode and custom interrupt packet enables in the UART custom
register block.
Registers are accessed only via the USB interface by the XR_SET_REG and XR_GET_REG commands listed
in Table 4. The register address offsets are given in Table 6, Table 7 and Table 15, and the register blocks
are given in Table 5.
3.1 UART Manager Registers
TABLE 6: UART MANAGER REGISTERS
ADDRESS
REGISTER NAME
BIT-7
BIT-6
BIT-5
BIT-4
BIT-3
BIT-2
BIT-1
BIT-0
0X10 FIFO_ENABLE_CHA
0
0
0
0
0
0
RX
TX
0X11 FIFO_ENABLE_CHB
0
0
0
0
0
0
RX
TX
0X18 RX_FIFO_RESET_CHA Bit-7
Bit-6
Bit-5
Bit-4
Bit-3
Bit-2
Bit-1
Bit-0
0X19 RX_FIFO_RESET_CHB Bit-7
Bit-6
Bit-5
Bit-4
Bit-3
Bit-2
Bit-1
Bit-0
0x1C TX_FIFO_RESET_CHA
Bit-7
Bit-6
Bit-5
Bit-4
Bit-3
Bit-2
Bit-1
Bit-0
0x1D TX_FIFO_RESET_CHB
Bit-7
Bit-6
Bit-5
Bit-4
Bit-3
Bit-2
Bit-1
Bit-0
3.1.1 FIFO_ENABLE Registers
Enables the RX FIFO and TX FIFOs. For proper functionality, the UART TX and RX must be enabled in the
following order:
FIFO_ENABLE_CHx = 0x1 // Enable TX FIFO
UART_ENABLE = 0x3
// Enable TX and RX of that channel
FIFO_ENABLE_CHx = 0x3 // Enable RX FIFO
3.1.2 RX_FIFO_RESET and TX_FIFO_RESET Registers
Writing a non-zero value to these registers resets the FIFOs.
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