Reset Initialization
MSC8144E Reference Manual, Rev. 3
Freescale Semiconductor
20-21
20.2.7.1 Idle Input Line Wake-Up (WAKE = 0)
In idle input line wake-up, an idle condition on
URXD
(all logic 1s) clears the SCICR[RWU] bit
and wakes up the SCI. The initial frame or frames of every message contain addressing
information. All receiver software evaluate the addressing information, and receivers for which
the message is addressed process the frames that follow. Any receiver for which a message is not
addressed can set its SCICR[RWU] bit and return to the standby state. The RWU bit remains set
and the receiver remains on standby until another idle character appears on
URXD
.
Idle line wake-up requires that messages be separated by at least one idle character and that no
message contain idle characters. The idle character that wakes a receiver does not set the receiver
idle bit, IDLE, or the receive data register full flag, SCISR[RDRF]. The idle line type bit,
SCICR[ILT], determines whether the receiver begins counting logic 1s as idle character bits after
the start bit or after the stop bit.
Note:
With the WAKE bit clear, setting the SCICR[RWU] bit after
URXD
has been idle can
cause the receiver to wake up immediately.
20.2.7.2 Address Mark Wake-Up (WAKE = 1)
In address mark wake-up, a logic 1 in the MSB position of a frame clears the SCICR[RWU] bit
and wakes up the SCI. This frame is considered to contain an address character. Hence, all data
characters should have their MSB at zero. Each receiver software evaluates the addressing
information when awakened and compares it to its own address. If the addresses match, the
receiver(s) process the frames that follow. If the addresses do not match, the receiver software
puts the receiver to sleep by setting the SCICR[RWU] bit. The RWU bit remains set and the
receiver remains on standby until another address frame appears on
URXD
.
The logic 1 in the MSB of an address character clears the receiver RWU bit before the stop bit is
received and sets the SCISR[RDRF] interrupt flag. Address mark wake-up allows messages to
contain idle characters but requires that the MSB be reserved for use in address frames.
20.3 Reset Initialization
After reset the UART transmitter and receiver are disabled and
UTXD
and
URXD
are not driven.
For information on initializing the transmitter, refer to Section 20.1.1. For information on
initializing the receiver, refer to Section 20.2.1.
Summary of Contents for MSC8144E
Page 1: ...MSC8144E Reference Manual Quad Core Media Signal Processor MSC8144ERM Rev 3 July 2009 ...
Page 48: ...MSC8144E Reference Manual Rev 3 xlviii Freescale Semiconductor ...
Page 86: ...MSC8144E Reference Manual Rev 3 1 38 Freescale Semiconductor Overview ...
Page 168: ...MSC8144E Reference Manual Rev 3 3 60 Freescale Semiconductor External Signals ...
Page 242: ...MSC8144E Reference Manual Rev 3 5 26 Freescale Semiconductor Reset ...
Page 314: ...MSC8144E Reference Manual Rev 3 8 24 Freescale Semiconductor General Configuration Registers ...
Page 414: ...MSC8144E Reference Manual Rev 3 10 14 Freescale Semiconductor MSC8144E SC3400 DSP Subsystem ...
Page 452: ...MSC8144E Reference Manual Rev 3 11 38 Freescale Semiconductor Internal Memory Subsystem ...
Page 520: ...MSC8144E Reference Manual Rev 3 12 68 Freescale Semiconductor DDR SDRAM Memory Controller ...
Page 1070: ...MSC8144E Reference Manual Rev 3 21 28 Freescale Semiconductor Timers ...