AT83SND2CMP3B datasheet(146/241 Pages) ATMEL

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146

4341F–MP3–03/06

AT8xC51SND2C/MP3B

Figure 18-17.

Data Block Transmission Flows

18.6.4

Data Receiver

18.6.4.1

Configuration

To receive data from the card you must first configure the data controller in reception mode by

clearing the DATDIR bit in MMCON1 register.

Figure 18-18 summarizes the data stream reception flows in both polling and interrupt modes

while Figure 18-19 summarizes the data block reception flows in both polling and interrupt

modes, these flows assume that block length is greater than 16 Bytes.

18.6.4.2

Data Reception

The end of a data frame (block or stream) reception is signalled to you by the EOFI flag in

MMINT register. This flag may generate an MMC interrupt request as detailed in Section "Inter-

rupt", page 148. When this flag is set, 2 other flags in MMSTA register: DATFS and CRC16S

give a status on the frame received. DATFS indicates if the frame format is correct or not: a valid

End bit has been received, and CRC16S indicates if the CRC16 computation is correct or not. In

case of data stream CRC16S has no meaning and stays cleared.

According to the MMC specification data transmission from the card starts after the access time

delay (formally N

AC parameter) beginning from the End bit of the read command. To avoid any

locking of the MMC controller when card does not send its data (e.g. physically removed from

the bus), you must launch a time-out period to exit from such situation. In case of time-out you

Data Block

Transmission

Start Transmission

DATEN = 1

DATEN = 0

FIFO Empty?

F1EI or F2EI = 1?

FIFO Filling

write 8 data to MMDAT

No More Data

To Send?

FIFOs Filling

write 16 data to MMDAT

a. Polling mode

Data Block

Initialization

Start Transmission

DATEN = 1

DATEN = 0

FIFOs Filling

write 16 data to MMDAT

Data Block

Transmission ISR

FIFO Filling

write 8 data to MMDAT

No More Data

To Send?

b. Interrupt mode

FIFO Empty?

F1EI or F2EI = 1?

Mask FIFOs Empty

F1EM = 1

F2EM = 1

Unmask FIFOs Empty

F1EM = 0

F2EM = 0

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