sc16c654 NXP Semiconductors, sc16c654 Datasheet - Page 13

• Manufacturer Part Number: sc16c654
• Description: Quad Uart With 64-byte Fifo And Infrared Irda Encoder/decoder
• Manufacturer: NXP Semiconductors

Philips Semiconductors
9397 750 11617
Product data
6.4 Internal registers
6.5 FIFO operation
The SC16C654/654D provides 15 internal registers for monitoring and control. These
registers are shown in
in the standard 16C554. These 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). Beyond the general 16C554
features and capabilities, the SC16C654/654D offers an enhanced feature register
set (EFR, Xon/Xoff1-2) that provides on-board hardware/software flow control.
Register functions are more fully described in the following paragraphs.
Table 5:
[1]
[2]
[3]
The 64-byte transmit and receive data FIFOs are enabled by the FIFO Control
Register (FCR) bit 0. With SC16C554 devices, the user can set the receive trigger
level, but not the transmit trigger level. The SC16C654/654D provides independent
trigger levels for both receiver and transmitter. To remain compatible with SC16C554,
the transmit interrupt trigger level is set to 8 following a reset. It should be noted that
the user can set the transmit trigger levels by writing to the FCR register, but
activation will not take place until EFR[4] is set to a logic 1. The receiver FIFO section
includes a time-out function to ensure data is delivered to the external CPU. An
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
Enhanced register set (EFR, Xon/off 1-2)
0
1
1
1
1
These registers are accessible only when LCR[7] is a logic 0.
These registers are accessible only when LCR[7] is a logic 1.
Enhanced Feature Register, Xon1, 2 and Xoff1, 2 are accessible only when the LCR is set to
“BF” (HEX).
A1
0
0
1
1
0
0
1
1
0
0
1
0
0
1
1
Internal registers decoding
Quad UART with 64-byte FIFO and infrared (IrDA) encoder/decoder
A0
0
1
0
1
0
1
0
1
0
1
0
0
1
0
1
Rev. 04 — 19 June 2003
READ mode
Receive Holding Register
Interrupt Status Register
Line Status Register
Modem Status Register
Scratchpad Register
LSB of Divisor Latch
MSB of Divisor Latch
Enhanced Feature Register
Xon1 word
Xon2 word
Xoff1 word
Xoff2 word
Table
5. Twelve registers are similar to those already available
[2]
[3]
SC16C654/654D
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
Enhanced Feature Register
Xon1 word
Xon2 word
Xoff1 word
Xoff2 word
© Koninklijke Philips Electronics N.V. 2003. All rights reserved.
[1]
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