MC9328MX1_06 Datasheet, PDF (74/100 Pages) Freescale Semiconductor, Inc – MX Family of applications processors

Functional Description and Application Information
Table 30. Timing Values for Figure 48 through Figure 52 (Continued)
Parameter
Symbol
Minimum
Maximum
Command read cycle
NRC
8
–
Command-command cycle
NCC
8
–
Command write cycle
NWR
2
–
Stop transmission cycle
NST
2
2
TAAC: Data read access time -1 defined in CSD register bit[119:112]
NSAC: Data read access time -2 in CLK cycles (NSAC·100) defined in CSD register bit[111:104]
Unit
Clock cycles
Clock cycles
Clock cycles
Clock cycles
4.10.2 SDIO-IRQ and ReadWait Service Handling
In SDIO, there is a 1-bit or 4-bit interrupt response from the SDIO peripheral card. In 1-bit mode, the
interrupt response is simply that the SD_DAT[1] line is held low. The SD_DAT[1] line is not used as data
in this mode. The memory controller generates an interrupt according to this low and the system interrupt
continues until the source is removed (SD_DAT[1] returns to its high level).
In 4-bit mode, the interrupt is less simple. The interrupt triggers at a particular period called the “Interrupt
Period” during the data access, and the controller must sample SD_DAT[1] during this short period to
determine the IRQ status of the attached card. The interrupt period only happens at the boundary of each
block (512 bytes).
CMD S T Content CRC E Z Z P S Response E Z Z Z
******
ZZZ
DAT[1]
For 4-bit
Interrupt Period
S Block Data E
IRQ
S Block Data E
IRQ
LH
DAT[1]
For 1-bit
Interrupt Period
Figure 53. SDIO IRQ Timing Diagram
ReadWait is another feature in SDIO that allows the user to submit commands during the data transfer. In
this mode, the block temporarily pauses the data transfer operation counter and related status, yet keeps
the clock running, and allows the user to submit commands as normal. After all commands are submitted,
the user can switch back to the data transfer operation and all counter and status values are resumed as
access continues.
MC9328MX1 Technical Data, Rev. 7
74
Freescale Semiconductor