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Freescale Semiconductor, Inc.

Freescale Semiconductor, Inc.

SERIAL COMMUNICATION INTERFACE (SCI)

6.3.8.1Transmitting Data and Address Characters

Transmitting data and address when the multidrop mode is selected is shown in Figure

6-30. The output sequence shown is idle line, data/address, and the next character. In both cases, an “A” is being transmitted. To send data, TE must be toggled to send the idle line, and then “A” must be sent to STX. Sending the “A” to the STX sets the ninth bit in the frame to zero, which indicates that this frame contains data. If the “A” is sent to STXA instead, the ninth bit in the frame is set to a one, which indicates that this frame contains an address.

6.3.8.2Wired-OR Mode

Building a multidrop bus network requires connecting multiple transmitters to a common wire. The wired-OR mode allows this to be done without damaging the transmitters when the transmitters are not in use. A protocol is still needed to prevent two transmitters from simultaneously driving the bus. The SCI multidrop word format provides an address field to support this protocol. Figure 6-31 shows a multidrop configuration using wired-OR (set bit 7 of the SCR). The protocol shown consists of an idle line between messages; each message begins with an address character. The message can be any length, depending on the protocol. Each processor in this system has one address that it responds to although each processor can be programmed to respond to more than one address.

6.3.8.3Idle Line Wakeup

A wakeup mode frees a DSP from reading messages intended for other processors. The usual operational procedure is for each DSP to suspend SCI reception (the DSP can continue processing) until the beginning of a message. Each DSP compares the address in the message header with the DSPs address. If the addresses do not match, the SCI again suspends reception until the next address. If the address matches, the DSP will read and process the message and then suspend reception until the next address.

The idle line wakeup mode wakes up the SCI to read a message before the first character arrives. This mode allows the message to be in any format.

Figure 6-32 shows how to configure the SCI to detect and respond to an idle line. The word format chosen (WDS2, WDS1, and WDS0 in the SCR) must be asynchronous. The

WAKE bit must be clear to select idle line wakeup, and RWU must be set to put the SCI to “sleep” and enable the wakeup function. RIE should be set if interrupts are to be used to receive data. If processing must occur when the idle line is first detected, ILIE should be set. The current message is followed by one or more data frames of ones (10 or 11 bits each, depending on which word format is used), which are detected as an idle line. If the word format is multidrop (an 11-bit code), after the 11 ones, the receiver determines the line is idle and (1) clears the RWU, enabling the receiver. The IDLE bit (2) and an internal flag SRIINT (3) are set, indicating the line is idle. The SCI is now ready to receive messages; however, nothing more will happen until the next start bit unless (4) ILIE is set.

MOTOROLA PORT C 6 - 57

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Freescale Semiconductor, Inc.

Freescale Semiconductor, Inc.

SERIAL COMMUNICATION INTERFACE (SCI)

 

 

 

 

 

 

NEXT

CHARACTER

ST

 

 

 

 

 

 

NEXT

CHARACTER

ST

 

 

 

 

 

 

 

 

 

 

 

 

0 0 STOP

 

DATA

 

 

 

 

 

 

0 1 STOP

 

ADDRESS

 

 

 

 

 

 

 

 

 

 

1

 

 

 

 

 

 

 

 

1

 

 

 

 

 

 

 

 

 

 

 

 

0

 

 

 

 

 

 

 

 

0

 

 

 

 

DATA

 

 

 

HIGHREGISTERDATA(WRITE ONLY)

MIDREGISTERDATA(WRITE ONY)

LOWREGISTERDATA(WRITE ONLY)

 

0

 

 

ADDRESS

 

 

 

 

 

0

 

(WRITEREGISTERDATAONLY)

 

AddressandCharacters

 

 

 

 

STLINEIDLE1 0 0 0

 

 

 

 

 

 

 

LINEIDLE

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

0

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

0

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

0

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

1

 

 

 

 

 

 

 

 

 

 

STXSCI TRANSMIT

 

 

 

 

 

 

 

 

 

 

ST

 

 

 

TransmittingData

 

 

 

0

SCI TRANSMIT

SCI TRANSMIT

 

TXD

0

STXA

0

 

 

STX

 

 

TXD

0

STXA

“A”

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

TRANSMITSCI

 

 

 

 

 

7

 

 

 

 

 

7

 

7

 

 

 

 

 

 

7

 

 

6-30

“A”

$41

01000001

8

 

STX

 

 

SHIFT REGISTER

8

 

8

 

STX

 

 

 

SHIFT REGISTER

8

 

 

Figure

 

 

 

16 15

STX

 

 

 

SCI TRANSMIT DATA

16 15

 

16 15

STX

 

 

 

 

SCI TRANSMIT DATA

16 15

 

 

 

 

 

 

23

 

 

 

 

 

23

 

23

 

 

 

 

 

 

23

 

 

 

 

 

 

 

X:$FFF6

X:$FFF5

X:$FFF4

 

 

 

X:$FFF3

 

X:$FFF6

X:$FFF5

X:$FFF4

 

 

 

 

X:$FFF3

 

 

6 - 58 PORT C MOTOROLA

For More Information On This Product, Go to: www.freescale.com

Freescale Semiconductor, Inc.

Freescale Semiconductor, Inc.

SERIAL COMMUNICATION INTERFACE (SCI)

 

SCICONTROLREGISTER(SCR) (READ/WRITE)

 

 

 

 

 

1K

AN MESSAGE D

 

 

THIRD CHARACTER

D0 D1

SECOND CHARACTER

OF MESSAGE D

 

5 4 3 2 1 0

WAKE SBK SSFTD 1 1 0

WDS2 WDS1 WDS0

DSP56002 DSP56002

SCI PORT SCI PORT

ADDRESS N-1 ADDRESS N

XMIT REC XMIT REC

 

A1 MESSAGE B

 

LINEIDLE WAKEUP AND/ORINTERRUPT WAKEUPCHARACTERADDRESS INTERRUPTAND/OR

SECOND CHARACTER

D0 D1 D2 D3 D4 D5 D6 D7 0

FIRST CHARACTER OF MESSAGE D

INDICATES A DATA CHARACTER

OR Mode

12131415 11 10 9 8 7 6

X:$FFF0TIETMIESTIRSCKP RIE ILIE TE RE 1 RWU

WOMS

DSP56002DSP56002 OTHER

PORTSCI SCI PORT SERIAL PORT

1ADDRESSADDRESS 2 ADDRESS 3

RECXMITXMIT REC XMIT REC

 

AMESSAGEA2 A3 MESSAGE C

IDLE

FIRST CHARACTER

IDLE

ADDRESS N

INDICATES AN ADDRESS CHARACTER

Figure 6-31 Wired-

 

 

 

 

 

 

 

 

 

 

 

 

1

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

N7

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

N6

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

N5

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

N4

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

N3

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

N2

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

N1

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

N0

 

 

 

MOTOROLA PORT C 6 - 59

For More Information On This Product, Go to: www.freescale.com

Freescale Semiconductor, Inc.

Freescale Semiconductor, Inc.

SERIAL COMMUNICATION INTERFACE (SCI)

 

 

 

SCICONTROLREGISTER(SCR) (READ/WRITE)

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

0

 

 

WDS0

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

1

 

 

WDS1

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

5 4 3 2

 

 

WDS2

 

 

 

MESSAGE B

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

SSFTD

 

 

 

 

 

 

 

 

 

 

HOW LONG IT LASTS.

 

 

 

 

 

 

 

 

 

 

 

 

A2

 

 

 

 

 

 

REGISTER (SSR)

 

 

 

 

SBK

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

0

 

WAKE

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

STATE,IDLENO MATTER

 

 

 

 

8 7 6

 

 

WOMSRETE 1

 

RWU

 

 

 

 

 

 

 

 

 

 

0

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

TRNETDRE (READONLY)

 

 

 

111213141510 9

 

 

 

RIEILIE

 

AMESSAGEA1

 

BITSSTOP11OR10FORIDLEISLINE

 

 

 

ENABLED.ISRECEIVERTHECLEARED;ISRWU1. LINETHEINDICATINGSSR,INSETISIDLE2.IS IDLE. GENERATEDISSRIINTFLAGINTERNALAN3. ONCE EACH

34567 2 1

STATUS SCI

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

X:$FFF0

 

 

X:$FFF1

 

 

 

 

 

 

 

 

 

 

 

(SRIINT)IDLE

 

 

1

 

 

 

 

 

 

 

 

 

 

 

 

 

 

RDRF

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

1

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

1

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

TIE

 

 

 

 

 

 

 

 

 

 

 

 

 

 

OR

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

PE

 

 

 

 

 

 

TMIE

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

FE

 

 

 

 

 

 

STIR

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

SCKP

 

 

 

 

 

 

 

 

 

 

 

 

 

 

R8

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

IDLE LINE

INTERRUPT SERVICE

ROUTINE

(FAST OR LONG)

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

SCI IDLE LINE

 

 

 

 

 

 

 

 

INTERRUPT VECTOR TABLE

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

P:$001A

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

IS PENDING.

AUTOMATICALLY CLEARED.

 

 

 

 

 

 

 

 

 

 

 

 

 

IDLE LINE INTERRUPT

ACCEPTED, SRIINT IS

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

= 1 IN SCR, THEN AN SCI

IDLE LINE INTERRUPT IS

 

 

 

 

 

 

 

 

 

 

 

 

 

IF ILIE

WHEN

 

 

 

 

 

 

 

 

 

 

 

 

4.

5.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Figure 6-32 Idle Line Wakeup

If ILIE is set, an SCI idle line interrupt will be recognized as pending. When the idle line

6 - 60 PORT C MOTOROLA

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