Specifications

56
AT83SND2CMP3
7524D–MP3–07/07
required, to provide 8 (eight) clock cycles for the card to complete the operation
before shutting down the clock. Following is a list of the various bus transactions:
• A command with no response. 8 clocks after the host command End bit.
• A command with response. 8 clocks after the card command End bit.
• A read data transaction. 8 clocks after the End bit of the last data block.
• A write data transaction. 8 clocks after the CRC status token.
• The host is allowed to shut down the clock of a “busy” card. The card will complete
the programming operation regardless of the host clock. However, the host must
provide a clock edge for the card to turn off its busy signal. Without a clock edge the
card (unless previously disconnected by a deselect command-CMD7) will force the
MDAT line down, forever.
Description The MMC controller interfaces to the C51 core through the following eight special func-
tion registers:
MMCON0, MMCON1, MMCON2, the three MMC control registers; MMSTA, the MMC
status register ; MMINT, the MMC interrupt register; MMMSK, the MMC interrupt mask
register; MMCMD, the MMC command register; MMDAT, the MMC data register; and
MMCLK, the MMC clock register.
As shown in Figure 45, the MMC controller is divided in four blocks: the clock generator
that handles the MCLK (formally the MMC CLK) output to the card, the command line
controller that handles the MCMD (formally the MMC CMD) line traffic to or from the
card, the data line controller that handles the MDAT (formally the MMC DAT) line traffic
to or from the card, and the interrupt controller that handles the MMC controller interrupt
sources. These blocks are detailed in the following sections.
Figure 45. MMC Controller Block Diagram
Clock Generator The MMC clock is generated by division of the oscillator clock (F
OSC
) issued from the
Clock Controller block as detailed in Section "Oscillator", page 10. The division factor is
given by MMCD7:0 bits in MMCLK register, a value of 0x00 stops the MMC clock.
Figure 46 shows the MMC clock generator and its output clock calculation formula.
OSC
CLOCK
MCMD
MCLK
8
Internal
Bus
MDAT
Command Line
Clock
MMC
Interrupt
Request
Generator
Controller
Data Line
Controller
Interrupt
Controller