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Enhanced Serial Communication Interface (eSCI)
PXN20 Microcontroller Reference Manual, Rev. 1
Freescale Semiconductor
31-29
31.4.5.2.2
Frame and Character Transmission
The transmitter starts the transmission of a data frame or special character when the condition for the
start
transition as described in
is fulfilled. There are three source for data or character transmission.
The priority among these source are specified in
. All three sources can be available at one
point in time.
31.4.5.2.3
CPU Controlled SCI Data Frame Transmission
The transmission of a data frame is started when the transmitter is in its ready state and only the commit
bit iCMT is set.
As the first step, the content of the eSCI SCI Data Register (eSCI_SDR) is transferred into the internal
transmitter shift register. When this transfer is finished, the internal commit bit iCMT is cleared and the
transmit data register empty flag TDRE in the eSCI Interrupt Flag and Status Register 1 (eSCI_IFSR1) is
set. If the transmit interrupt enable bit TIE in the eSCI Control Register 1 (eSCI_CR1) is also set, the
TDRE flag generates a transmitter interrupt request.
The transmitter shift register then shifts a frame out through the TXD output signal, which is prefaced with
a start bit and appended with the parity bit, if configured, and the configured number of stop bits.
When the last stop bit has been transmitted and the application has not disabled the transmitter, the
transmitter returns to the ready state via the
done
transition. If no frame or character transmit request is
pending, the transfer complete flag TC in the eSCI Interrupt Flag and Status Register 1 (eSCI_IFSR1) is
set.
If the application has disabled the transmitter while the frame is transmitted and stop bit has been
transmitted, the transmitter goes into the idle state via the
halt
transition. The transfer complete flag TC in
Table 31-24. Transmitter Module Transitions
Transition
Condition
Action
Description
start
(State = Ready)
and
(SBK = 1 or iPRE = 1 or iCMT = 1)
TACT = 1
Start of transmission of data frame or special character
when data are available or character transmission
request is pending.
done
State = Run
and
last stop bit transmitted
TACT = 0
TC =
(SBK & iPRE & TC)
Finished transmission of data frame or special
character and transmitter still enabled. Transmission is
complete if no transmit request is pending.
halt
State = Stop
and
last stop bit transmitted
TACT = 0
TC = 1
iCMT = 0
Finished transmission of data frame or special
character and transmitter was disabled.
Table 31-25. Transmit Source Priority
Priority
Indication
Transmission Source
(highest) 0
eSCI_CR1[SBK] = 1
Break character.
1
iPRE = 1 Preamble.
(lowest) 2
iCMT = 1
eSCI SCI Data Register (eSCI_SDR) frame.
Summary of Contents for PXN2020
Page 1: ...PXN20 Microcontroller Reference Manual Devices Supported PXN2020 PXN2120 PXN20RM Rev 1 06 2011...
Page 42: ...PXN20 Microcontroller Reference Manual Rev 1 lxiv Freescale Semiconductor...
Page 64: ...Introduction PXN20 Microcontroller Reference Manual Rev 1 1 22 Freescale Semiconductor...
Page 112: ...Signal Description PXN20 Microcontroller Reference Manual Rev 1 3 44 Freescale Semiconductor...
Page 118: ...Resets PXN20 Microcontroller Reference Manual Rev 1 4 6 Freescale Semiconductor...
Page 372: ...e200z6 Core Z6 PXN20 Microcontroller Reference Manual Rev 1 13 8 Freescale Semiconductor...
Page 412: ...e200z0 Core Z0 PXN20 Microcontroller Reference Manual Rev 1 14 14 Freescale Semiconductor...
Page 821: ...Media Local Bus MLB PXN20 Microcontroller Reference Manual Rev 1 Freescale Semiconductor 27 49...
Page 822: ...Media Local Bus MLB PXN20 Microcontroller Reference Manual Rev 1 27 50 Freescale Semiconductor...
Page 1376: ...Memory Map PXN20 Microcontroller Reference Manual Rev 1 A 118 Freescale Semiconductor...