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194

AT85C51SND3Bx

7632A–MP3–03/06

Data Line Controller As shown in Figure 89, the data line controller is based on a 16-Byte FIFO used both by

the data transmitter channel and by the data receiver channel.

Data transfer can be handled in transmission or received by the Data Flow Controller

(see

Section “Data Flow Controller”, page 78) or by the C51 using MMDAT register.

Figure 89. Data Line Controller Block Diagram

Bus Width Control The data line controller supports the SD card and the new MMC 4.0 4-bit bus mode

allowing higher transfer rate. The 4-bit bus width is controlled by software by setting the

DBSIZE1:0 bits in MMCON2 register according to

Table 219. In case of 1-bit bus width

(card default), SDDAT0 is used as SDDAT line and SDDAT3:1 lines are released as I/O

port.

Table 219. Data Bus Size

FIFO Implementation The 16-Byte FIFO is managed using 1 pointer and four flags indicating the status ready

of whole or half FIFO.

Pointer value is not accessible by software but can be reset at any time by setting and

clearing DPTRR bit in MMCON0 register. Resetting the pointer is equivalent to abort the

writing or reading of data.

FIFO flags indicate when FIFO is ready to be read in receive mode or to be written in

transmit mode. WFRI is set when 16 bytes are available in writing or reading. HFRI is

set when 8 bytes are available. These flags are cleared when read. These flags may

generate an interrupt request as detailed in

Section “Interrupt”. WFRS and HFRS give

the status of the FIFO. They are set when respectively 16 bytes or 8 bytes are ready to

be read or written depending on the receive or transmit mode.

DATFS

MMSTA.3

CRC16S

MMSTA.4

HFRS

MMSTA.0

HFRI

MMINT.2

DFMT

MMCON0.2

MBLOCK

MMCON0.3

DATDIR

MMCON1.3

Data Converter

// -> 1-bit/4-bit

BLEN11:0

MMCON1.7:4

DATEN

MMCON1.2

DATA Line

Finished State Machine

Data Converter

1-bit/4-bit -> //

DPTRR

MMCON0.6

TX/RX Ptr

WFRI

MMINT.3

CRC16 and Format

Checker

WFRS

MMSTA.1

EOFI

MMINT.4

CBUSY

MMSTA.5

SDDAT3

DBSIZE1:0

MMCON2.4:3

CRC16

Generator

MMBLP7:0

EOBI

MMINT.1

FIFO

16-Byte

MMDAT

DBSIZE1:0 Bus Size

0 1-bit SDDAT0 data bus.

1 4-bit SDDAT3:0 data bus.

2-3 Reserved for future use, do not program these values.

1 2 ... 189 190 191 192 193 194 195 196 197 198 199 ... 262 263

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