AT85C51SND3B Datasheet, PDF (199/270 Pages) ATMEL Corporation – Single-Chip Digital Audio Decoder - Encoder with USB 2.0 Interface

Figure 92. Data Block Transmission Flows
Data Block
Transmission
Start Transmission
DATEN = 1
FIFO Filling
write 16 data to MMDAT
FIFO Empty?
HFRS = 1?
FIFO Filling
write 8 data to MMDAT
No More Data
To Send?
AT85C51SND3B
Data Block
Initialization
Start Transmission
DATEN = 1
Unmask FIFO Empty
HFRM = 0
FIFO Filling
write 16 data to MMDAT
Data Block
Transmission ISR
FIFO Empty?
HFRI = 1?
FIFO Filling
write 8 data to MMDAT
No More Data
To Send?
Mask FIFO Empty
HFRM = 1
b. Interrupt mode
a. Polling mode
Data Receiver
Configuration
Data Reception
To receive data from the card the data controller must be configured in reception mode
by clearing the DATDIR bit in MMCON1 register.
Figure 93 summarizes the data stream reception flows in both polling and interrupt
modes while Figure 94 summarizes the data block reception flows in both polling and
interrupt modes, these flows assume that block length is greater than 16 Bytes.
Reception is enabled by setting DATEN bit in MMCON1 register. The end of a data
frame (block(s) or stream) reception is signalled by the EOFI flag in MMINT register. In
multiblock mode, OEBI flag signals the reception of one block. These flags may gener-
ate an interrupt request as detailed in Section “Interrupt”. When EOFI 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. CRC16S must by
reset by software by setting DCR bit in MMCON2 register. In case of data stream
CRC16S has no meaning and stays cleared. DATEN flag is cleared when EOFI is set.
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 com-
mand. To avoid any locking of the MMC controller when card does not send its data
(e.g. physically removed from the bus), a time-out timer must be launched to recover
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