Rainbow Electronics AT89C51SND1C - Manual (Page 121)

121
AT8xC51SND1C
4109E–8051–06/03
Figure 86. Data Block Transmission Flows
Data Receiver
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 87 summarizes the data stream reception flows in both polling and interrupt
modes while Figure 88 summarizes the data block reception flows in both polling and
interrupt modes, these flows assume that block length is greater than 16 Bytes.
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 Sec-
tion "Interrupt", page 124. 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 com-
mand. 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 may reset the data controller and its internal state
machine by setting and clearing the DCR bit in MMCON2 register.
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