NXP Semiconductors LPC24XX UM10237 - Manual (Page 567)

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User manual Rev. 04 — 26 August 2009 567 of 792
NXP Semiconductors
UM10237
Chapter 21: LPC24XX SD/MMC card interface
The card status size can be 32 or 127 bits, depending on the response type (see
Table 21–498 ).
The most significant bit of the card status is received first. The MCIResponse3 register
LSBit is always 0.
6.7 Data Timer Register (MCIDataTimer - 0xE008 C024)
The MCIDataTimer register contains the data timeout period, in card bus clock periods.
Table 21–499 shows the bit assignment of the MCIDataTimer register.
A counter loads the value from the data timer register, and starts decrementing when the
Data Path State Machine (DPSM) enters the WAIT_R or BUSY state. If the timer reaches
0 while the DPSM is in either of these states, the timeout status flag is set.
A data transfer must be written to the data timer register and the data length register
before being written to the data control register.
6.8 Data Length Register (MCIDataLength - 0xE008 C028)
The MCIDataLength register contains the number of data bytes to be transferred. The
value is loaded into the data counter when data transfer starts.
Table 21–500 shows the
bit assignment of the MCIDataLength register.
For a block data transfer, the value in the data length register must be a multiple of the
block size (see
Section 21–6.9 “Data Control Register (MCIDataCtrl - 0xE008 C02C)” ).
To initiate a data transfer, write to the data timer register and the data length register
before writing to the data control register.
Table 497: Response registers (MCIResponse0-3 - addresses 0xE008 0014, 0xE008 C018,
0xE008 001C and 0xE008 C020) bit description
Bit Symbol Description Reset Value
31:0 Status Card status 0x0000 0000
Table 498: Response Register Type
Description Short Response Long Response
MCIResponse0 Card status [31:0] Card status [127:96]
MCIResponse1 Unused Card status [95:64]
MCIResponse2 Unused Card status [63:32]
MCIResponse3 Unused Card status [31:1]
Table 499: Data Timer register (MCIDataTimer - address 0xE008 C024) bit description
Bit Symbol Description Reset Value
31:0 DataTime Data timeout period. 0x0000 0000
Table 500: Data Length register (MCIDataLength - address 0xE008 C028) bit description
Bit Symbol Description Reset
Value
15:0 DataLength Data length value 0x0000
31:16 - Reserved, user software should not write ones to reserved bits.
The value read from a reserved bit is not defined. NA