Zilog Z16C35 Manual do Utilizador descarregar pdf (Página 249)

Application Note

Serial Communication Controller (SCC

™

): SDLC Mode of Operation

11-6

RECEIVE INTERRUPTS ON FIRST CHARACTER OR SPECIAL CONDITIONS

The sequence of events in this mode is similar to that in

“Receive Interrupts on all received characters and Special

Conditions”, except that it generates Receive Character

Interrupt on the first received character only, and

subsequent data is read by the DMA.

The SCC is placed in this mode by programming Bit D4-3

of WR1 to 01. Once programmed in this mode, the SCC

generates interrupts when it receives the First Character of

the packet or a Special Condition occurs. This mode is for

operation with the DMA. On the interrupt for the first

received character, DMA is enabled. On Special

Conditions (either End-of-Message, overrun, or Parity

error, — parity on the SDLC is not normal, however), the

service routine stops the DMA and starts over again.

Figure 3. Typical SDLC Receive Sequence with Receive Interrupts on First Character or Special Condition

RxCLK

Rx Data

Opening Flag

Data 81H Data 42H

Data 0FFH

Data 42H

CRC 0E013H

Closing Flag

Note 9

/INT

Note 3

➘

Note 3

➘

Note 5

➘

Note 7

➘

Note 1

Note 6

➘

Note 8

➘

Note 10

➘

Note 12

➘

/W//REQ (In /REQ mode)

/SYNC

➘

Note 2

Note 9

➘

Note 4

➘

Note 11

➘

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