Figure 68 – Rainbow Electronics AT89C5132 User Manual
Page 94
94
AT8xC5132
4173A–8051–08/02
Figure 68. Data Block Transmission Flows
Data Receiver
Configuration
To receive data from the card, the user must first configure the data controller in recep-
tion mode by clearing the DATDIR bit in MMCON1 register.
Figure 69 summarizes the data stream reception flows in both polling and interrupt
modes while Figure 70 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 data frame (block or stream) reception is signalled by the EOFI flag in
MMINT register. This flag may generate an MMC interrupt request as detailed in Section
"Interrupt", page 97. When this flag is set, two 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, 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. phys-
ically removed from the bus), the user must launch a time-out period to exit from such
situation. In case of time-out the user 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