XR16L2550IM-F Datasheet, PDF (20/44 Pages) Exar Corporation – LOW VOLTAGE DUART WITH 16-BYTE FIFO

XR16L2550
LOW VOLTAGE DUART WITH 16-BYTE FIFO
REV. 1.1.3
3.0 UART INTERNAL REGISTERS
Each of the UART channel in the L2550 has its own set of configuration registers selected by address lines A0,
A1 and A2 with CSA# or CSB# selecting the channel. The registers are 16C550 compatible. The complete
register set is shown on Table 7 and Table 8.
TABLE 7: UART CHANNEL A AND B UART INTERNAL REGISTERS
A2,A1,A0 ADDRESSES
REGISTER
READ/WRITE
COMMENTS
16C550 COMPATIBLE REGISTERS
0 00
RHR - Receive Holding Register
THR - Transmit Holding Register
Read-only
Write-only
LCR[7] = 0
0 00
0 01
DLL - Div Latch Low Byte
DLM - Div Latch High Byte
Read/Write
Read/Write
LCR[7] = 1, LCR ≠ 0xBF
0 00
0 01
DREV - Device Revision
DVID - Device ID
Read/Write
Read/Write
LCR[7] = 1, LCR ≠ 0xBF,
DLL = 0x00, DLM = 0x00
0 01
IER - Interrupt Enable Register
Read/Write
LCR[7] = 0
0 10
ISR - Interrupt Status Register
FCR - FIFO Control Register
Read-only
Write-only
LCR ≠ 0xBF
0 11
LCR - Line Control Register
Read/Write
1 00
MCR - Modem Control Register
Read/Write
1 01
1 10
LSR - Line Status Register
Reserved
MSR - Modem Status Register
Reserved
Read-only
Write-only
Read-only
Write-only
LCR ≠ 0xBF
1 11
SPR - Scratch Pad Register
Read/Write
ENHANCED REGISTERS
0 10
EFR - Enhanced Function Register
Read/Write
1 00
Xon-1 - Xon Character 1
Read/Write
1 01
Xon-2 - Xon Character 2
Read/Write
LCR = 0xBF
1 10
Xoff-1 - Xoff Character 1
Read/Write
1 11
Xoff-2 - Xoff Character 2
Read/Write
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