
XR20V2170
21
REV. 1.0.1
I2C/SPI UART WITH 64-BYTE FIFO AND RS232 TRANSCEIVER
4.0 INTERNAL REGISTER DESCRIPTIONS
4.1
Receive Holding Register (RHR) - Read- Only
4.2
Transmit Holding Register (THR) - Write-Only
4.3
Interrupt Enable Register (IER) - Read/Write
The Interrupt Enable Register (IER) masks the interrupts from receive data ready, transmit empty, line status
and modem status registers. These interrupts are reported in the Interrupt Status Register (ISR).
0x0A
IODir
RD/WR
0
1
0
Bit-3
Bit-2
Bit-1
Bit-0
0x0B
IOState RD/WR
0
Bit-3
Bit-2
Bit-1
Bit-0
0x0C IOIntEna RD/WR
0
Bit-3
Bit-2
Bit-1
Bit-0
0x0D reserved
-
0
0x0E IOControl RD/WR
0
UART
SW
Reset
0
1
IOLatch
0x0F
EFCR
RD/WR
0
TX
Disable
RX
Disable
0
Baud Rate Generator Divisor
0x00
DLL
RD/WR
Bit-7
Bit-6
Bit-5
Bit-4
Bit-3
Bit-2
Bit-1
Bit-0
LCR[7]=1
LCR
≠0xBF
0x01
DLM
RD/WR
Bit-7
Bit-6
Bit-5
Bit-4
Bit-3
Bit-2
Bit-1
Bit-0
0x02
DLD
RD/WR
Bit-7
Bit-6
4X
Mode
8X Mode
Frac-
tional
Divisor
Bit-3
Frac-
tional
Divisor
Bit-2
Frac-
tional
Divisor
Bit-1
Frac-
tional
Divisor
Bit-0
LCR[7]=1
LCR
≠0xBF
EFR[4]=1
Enhanced Registers
0x02
EFR
RD/WR
Auto
CTS
Enable
Auto RTS
Enable
Special
Char
Select
Enable
IER [7:4],
ISR [5:4],
FCR[5:4],
MCR[7:5],
DLD
Soft-
ware
Flow
Cntl
Bit-3
Soft-
ware
Flow
Cntl
Bit-2
Soft-
ware
Flow
Cntl
Bit-1
Soft-
ware
Flow
Cntl
Bit-0
LCR=0XBF
0x04
XON1
RD/WR
Bit-7
Bit-6
Bit-5
Bit-4
Bit-3
Bit-2
Bit-1
Bit-0
0x05
XON2
RD/WR
Bit-7
Bit-6
Bit-5
Bit-4
Bit-3
Bit-2
Bit-1
Bit-0
0x06
XOFF1
RD/WR
Bit-7
Bit-6
Bit-5
Bit-4
Bit-3
Bit-2
Bit-1
Bit-0
0x07
XOFF2
RD/WR
Bit-7
Bit-6
Bit-5
Bit-4
Bit-3
Bit-2
Bit-1
Bit-0
TABLE 8: INTERNAL REGISTERS DESCRIPTION. SHADED BITS ARE ENABLED WHEN EFR BIT-4=1
ADDR
REG
NAME
READ/
WRITE
BIT-7
BIT-6
BIT-5
BIT-4
BIT-3
BIT-2
BIT-1
BIT-0
COMMENT