at85c51snd3b ATMEL Corporation, at85c51snd3b Datasheet - Page 193

• Manufacturer Part Number: at85c51snd3b
• Description: Single-chip Digital Audio Decoder - Encoder With Usb 2.0 Interface
• Manufacturer: ATMEL Corporation

Command Transmitter
7632C–MP3–11/06
tion from the card through the SDCMD line. These channels are detailed in the following
sections.
Figure 87. Command Line Controller Block Diagram
For sending a command to the card, the command index (1 Byte) and argument (4
Bytes) must be loaded in the command transmit FIFO using the MMCMD register.
Before starting transmission by setting the TXCEN bit in MMCON1 register, software
must first configure:
•
•
•
Figure 88 summarizes the command transmission flow.
The TXCEN flag is set until the end of transmission. The end of the command transmis-
sion is signalled by the EOCI flag in MMINT register becoming set. This flag may
generate an interrupt request as detailed in Section “Interrupt”. The end of the command
transmission also clears the TXCEN flag.
Command loading may be aborted by setting and clearing the CTPTR bit in MMCON0
register which resets the write pointer to the transmit FIFO.
Command Transmitter
Command Receiver
RX Pointer
TX Pointer
MMCON0.4
MMCON0.5
CRPTR
CTPTR
RXCEN bit in MMCON1 register to indicate whether a response is expected or not.
RFMT bit in MMCON0 register to indicate the response size expected.
CRCDIS bit in MMCON0 register to indicate whether the CRC7 included in the
response will be computed or not. In order to avoid CRC error, CRCDIS may be set
for response that do not include CRC7.
MMCMD
MMCMD
17-Byte
17-Byte
Write
Read
FIFO
FIFO
MMCON1.0
TXCEN
Data Converter
Data Converter
MMCON1.1
RXCEN
// -> Serial
Serial -> //
Finished State Machine
Finished State Machine
TX COMMAND Line
RX COMMAND Line
MMCON0.1
RFMT
MMSTA.2
CRC7S
CRC7 and Format
Generator
MMCON0.0
CRCDIS
CRC7
Checker
AT85C51SND3B
RESPFS
MMSTA.1
MMINT.5
MMINT.6
EOCI
EORI
SDCMD
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