sc68c2550b NXP Semiconductors, sc68c2550b Datasheet - Page 8

• Manufacturer Part Number: sc68c2550b
• Description: Sc68c2550b 5 V, 3.3 V And 2.5 V Dual Uart, 5 Mbit/s Max. , With 16-byte Fifos And Motorola Up Interface
• Manufacturer: NXP Semiconductors

Philips Semiconductors
9397 750 14941
Product data sheet
6.2 Internal registers
6.3 FIFO operation
The SC68C2550B 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
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).
Table 4:
[1]
[2]
The 16 byte transmit and receive data FIFOs are enabled by the FIFO Control Register
(FCR) bit 0. The user can set the receive trigger level via FCR[7:6], but not the transmit
trigger level. The receiver FIFO section includes a time-out function to ensure data is
delivered to the external CPU. An interrupt is generated whenever the Receive Holding
Register (RHR) has not been read following the loading of a character or the receive
trigger level has not been reached.
Table 5:
A2
General register set (THR/RHR, IER/ISR, MCR/MSR, FCR, LSR, SPR)
0
0
0
0
1
1
1
1
Baud rate register set (DLL/DLM)
0
0
Selected trigger level (characters)
1
4
8
14
These registers are accessible only when LCR[7] is a logic 0.
These registers are accessible only when LCR[7] is a logic 1.
A1
0
0
1
1
0
0
1
1
0
0
Internal registers decoding
Flow control mechanism
A0
0
1
0
1
0
1
0
1
0
1
5 V, 3.3 V and 2.5 V dual UART, 5 Mbit/s (max.), with 16-byte FIFOs
Read mode
Receive Holding Register
Interrupt Enable Register
Interrupt Status Register
Line Control Register
Modem Control Register
Line Status Register
Modem Status Register
Scratchpad Register
LSB of Divisor Latch
MSB of Divisor Latch
Rev. 02 — 28 April 2005
[2]
Table
IRQ pin activation
1
4
8
14
4. The UART registers function as data holding
Write mode
Transmit Holding Register
Interrupt Enable Register
FIFO Control Register
Line Control Register
Modem Control Register
n/a
n/a
Scratchpad Register
LSB of Divisor Latch
MSB of Divisor Latch
© Koninklijke Philips Electronics N.V. 2005. All rights reserved.
SC68C2550B
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