AT83SND2C_06 Datasheet, PDF (146/241 Pages) ATMEL Corporation – Single-Chip Flash Microcontroller with MP3 Decoder with Full Audio Interface

Figure 18-17. Data Block Transmission Flows
Data Block
Transmission
FIFOs Filling
write 16 data to MMDAT
Start Transmission
DATEN = 1
DATEN = 0
FIFO Empty?
F1EI or F2EI = 1?
FIFO Filling
write 8 data to MMDAT
No More Data
To Send?
Data Block
Initialization
FIFOs Filling
write 16 data to MMDAT
Unmask FIFOs Empty
F1EM = 0
F2EM = 0
Start Transmission
DATEN = 1
DATEN = 0
Data Block
Transmission ISR
FIFO Empty?
F1EI or F2EI = 1?
FIFO Filling
write 8 data to MMDAT
No More Data
To Send?
Mask FIFOs Empty
F1EM = 1
F2EM = 1
b. Interrupt mode
a. Polling mode
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
146 AT8xC51SND2C/MP3B
4341F–MP3–03/06