Philips Semiconductors
SC16C2550
Dual UART with 16 bytes of transmit and receive FIFOs and IrDA
encoder/decoder
Product data
Rev. 03 — 19 June 2003
10 of 46
9397 750 11621
© Koninklijke Philips Electronics N.V. 2003. All rights reserved.
6.2 Internal registers
The SC16C2550 provides two sets of internal registers (A and B) consisting of
12 registers each for monitoring and controlling the functions of each channel of the
UART. These registers are shown in
. The UART registers function as data
holding registers (THR/RHR), interrupt status and control registers (IER/ISR), a FIFO
control register (FCR), line status and control registers (LCR/LSR), modem status
and control registers (MCR/MSR), programmable data rate (clock) control registers
(DLL/DLM), and a user accessible scratchpad register (SPR).
[1]
These registers are accessible only when LCR[7] is a logic 0.
[2]
These registers are accessible only when LCR[7] is a logic 1.
[3]
Enhanced Feature Register, Xon1, 2 and Xoff1, 2 are accessible only when the LCR is set to
‘BF(HEX)’.
Table 3:
Serial port selection
Chip Select
Function
CSA-CSB = 1
none
CSA = 0
UART channel A
CSB = 0
UART channel B
Table 4:
Internal registers decoding
A2
A1
A0
READ mode
WRITE mode
General register set (THR/RHR, IER/ISR, MCR/MSR, FCR, LSR, SPR)
0
0
0
Receive Holding Register
Transmit Holding Register
0
0
1
Interrupt Enable Register
0
1
0
Interrupt Status Register
FIFO Control Register
0
1
1
Line Control Register
1
0
0
Modem Control Register
1
0
1
Line Status Register
n/a
1
1
0
Modem Status Register
n/a
1
1
1
Scratchpad Register
Scratchpad Register
Baud rate register set (DLL/DLM)
0
0
0
LSB of Divisor Latch
LSB of Divisor Latch
0
0
1
MSB of Divisor Latch
MSB of Divisor Latch
Enhanced register set (EFR, Xon/off 1-2)
0
1
0
Enhanced Feature Register
Enhanced Feature Register
1
0
0
Xon1 word
Xon1 word
1
0
1
Xon2 word
Xon2 word
1
1
0
Xoff1 word
Xoff1 word
1
1
1
Xoff2 word
Xoff2 word