MMC/SD Host Controller
7-144
This 16-bit register specifies the maximum number of clock cycles before a
data time-out condition occurs.
Table 7–104. MMC Data Time-out Register (MMC_DTO)
Bit
Name
Description
15–0
DTO
Data read time-out
Data Time-out Value (DTO)
In MMC/SD mode, the local host sets this field (bits 15-0) based on N
AC
clock
cycles. N
AC
is computed from the parameters TAAC and NSAC and the
operating clock frequency.
TAAC and NSAC are CSD card parameters and can be obtained by reading
the response register after a successful execution of a SEND_CSD command
(CMD9).
If the card does not respond within the specified number of cycles, data time-
out gets set to 1 in MMC_STAT[5] register bit.
The effective number of clock cycles for time-out value are to be multiplied by
1024 if MMC_SDIO:DTO_PS_En=1 and by 1 if DTO_PS_En=0.
In SPI mode, a data time-out condition is also generated if the RDY/BUSY
signal is asserted low (BUSY) for DTO consecutive clocks cycles (see
Table 7–105).
Table 7–105. Data Time-out Conditions
DTO
DTO_PS_En=0
DTO_PS_En=1
0x0000
No time-out
No time-out
0x0001
1
1024
MMC clock cycles
0x0002
2
2048
…
…
…
0xFFFF
65535 (2
16
-1)
67107840 (2
26
-2
10
)
Values after reset are low (all 16 bits).