SC16C654BIB64 PHILIPS [NXP Semiconductors], SC16C654BIB64 Datasheet - Page 25

• Manufacturer Part Number: SC16C654BIB64
• Description: 5 V, 3.3 V and 2.5 V quad UART, 5 Mbit/s (max.), with 64-byte FIFOs and infrared (IrDA) encoder/decoder
• Manufacturer: PHILIPS [NXP Semiconductors]

Philips Semiconductors
9397 750 14965
Product data sheet
7.1 Transmit (THR) and Receive (RHR) Holding Registers
7.2 Interrupt Enable Register (IER)
The serial transmitter section consists of an 8-bit Transmit Hold Register (THR) and
Transmit Shift Register (TSR). The status of the THR is provided in the Line Status
Register (LSR). Writing to the THR transfers the contents of the data bus (D7 to D0) to the
THR, providing that the THR or TSR is empty. The THR empty flag in the LSR register will
be set to a logic 1 when the transmitter is empty or when data is transferred to the TSR.
Note that a write operation can be performed when the THR empty flag is set
(logic 0 = FIFO full; logic 1 = at least one FIFO location available).
The serial receive section also contains an 8-bit Receive Holding Register (RHR).
Receive data is removed from the SC16C654B/654DB and receive FIFO by reading the
RHR register. The receive section provides a mechanism to prevent false starts. On the
falling edge of a start or false start bit, an internal receiver counter starts counting clocks
at the 16 clock rate. After 7
the start bit. At this time the start bit is sampled, and if it is still a logic 0 it is validated.
Evaluating the start bit in this manner prevents the receiver from assembling a false
character. Receiver status codes will be posted in the LSR.
The Interrupt Enable Register (IER) masks the interrupts from receiver ready, transmitter
empty, line status and modem status registers. These interrupts would normally be seen
on the INTA to INTD output pins in the 16 mode, or on wire-OR IRQ output pin in the
68 mode.
Table 9:
Bit
7
6
5
4
3
Symbol
IER[7]
IER[6]
IER[5]
IER[4]
IER[3]
Interrupt Enable Register bits description
Description
CTS interrupt.
RTS interrupt.
Xoff interrupt.
Sleep mode.
Modem Status Interrupt.
5 V, 3.3 V and 2.5 V quad UART, 5 Mbit/s (max.) with 64-byte FIFOs
logic 0 = disable the CTS interrupt (normal default condition)
logic 1 = enable the CTS interrupt. The SC16C654B/654DB issues an
interrupt when the CTS pin transitions from a logic 0 to a logic 1.
logic 0 = disable the RTS interrupt (normal default condition)
logic 1 = enable the RTS interrupt. The SC16C654B/654DB issues an
interrupt when the RTS pin transitions from a logic 0 to a logic 1.
logic 0 = disable the software flow control, receive Xoff interrupt (normal
default condition)
logic 1 = enable the software flow control, receive Xoff interrupt. See
6.5 “Software flow control”
logic 0 = disable Sleep mode (normal default condition)
logic 1 = enable Sleep mode. See
logic 0 = disable the modem status register interrupt (normal default
condition)
logic 1 = enable the modem status register interrupt
Rev. 02 — 20 June 2005
1
2
clocks, the start bit time should be shifted to the center of
for details.
SC16C654B/654DB
Section 6.11 “Sleep mode”
© Koninklijke Philips Electronics N.V. 2005. All rights reserved.
for details.
Section
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