SD/MMC/SDIO Registers

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SD_xxx is used to access onboard eMMC and external SD card slot (as selected via SD_CARD_PORT_SELECT).
SDIO_xxx is used to access the Atheros Wifi unit.


 ARM7 DSi SD/MMC Registers for Memory Card access (SD Card and onboard eMMC)
 4004800h 2    SD_CMD              Command and Response/Data Type
 4004802h 2    SD_CARD_PORT_SELECT   (SD/MMC:020Fh, SDIO:010Fh)
 4004804h 4    SD_CMD_PARAM0-1     Argument (32bit, 2 halfwords)
 400480Ah 2    SD_DATA16_BLK_COUNT        "Transfer Block Count"
 400480Ch 16   SD_RESPONSE0-7 (128bit, 8 halfwords)
 400481Ch 4    SD_IRQ_STATUS0-1  ;IRQ Status  (0=ack, 1=req)
 4004820h 4    SD_IRQ_MASK0-1    ;IRQ Disable (0=enable, 1=disable)
 4004824h 2    SD_CARD_CLK_CTL Card Clock Control
 4004826h 2    SD_DATA16_BLK_LEN  Memory Card Transfer Data Length
 4004828h 2    SD_CARD_OPTION Memory Card Option Setup (can be C0FFh)
 400482Ah 2    Fixed always zero?
 400482Ch 4    SD_ERROR_DETAIL_STATUS0-1   Error Detail Status
 4004830h 2    SD_DATA16_FIFO        Data Port  (SD_FIFO?)
 4004832h 2    Fixed always zero?   ;(TC6371AF:BUF1 Data MSBs?)
 4004834h 2    ? SD_TRANSACTION_CTL  Transaction Control
 4004836h 2    ? SD_CARD_INTERRUPT_CONTROL ;4004A36h used in SDIO IRQ handler
 4004838h 2    ? SD_CLK_AND_WAIT_CTL       ;4004A38h used in SDIO IRQ handler
 400483Ah 2    Fixed always zero?   ;(SDCTL_SDIO_HOST_INFORMATION)
 400483Ch 2    Fixed always zero?   ;(SDCTL_ERROR_CONTROL)
 400483Eh 2    Fixed always zero?   ;(TC6387XB: LED_CONTROL)
 4004840h 2    Fixed always 003Fh?
 4004842h 2    Fixed always 002Ah?
 4004844h 6Eh  Fixed always zerofilled?
 40048B2h 2    Fixed always FFFFh?
 40048B4h 6    Fixed always zerofilled?
 40048BAh 2    Fixed always 0200h?
 40048BCh 1Ch  Fixed always zerofilled?
 40048D8h 2    SD_DATA_CTL
 40048DAh 6    Fixed always zerofilled?
 40048E0h 2    SD_SOFT_RESET  Software Reset (bit0=SRST=0=reset)
 40048E2h 2    Fixed always 0009h?  ;(RESERVED2/9, TC6371AF:CORE_REV)
 40048E4h 2    Fixed always zero?
 40048E6h 2    Fixed always zero?   ;(RESERVED3, TC6371AF:BUF_ADR)
 40048E8h 2    Fixed always zero?   ;(TC6371AF:Resp_Header)
 40048EAh 6    Fixed always zerofilled?
 40048F0h 2    Fixed always zero?   ;(RESERVED10)
 40048F2h 2    ? Can be 0003h
 40048F4h 2    ? Can be 0770h
 40048F6h 2    ? Firmware tests bit0 (but, always 0?)       (RESERVED4)
 40048F8h 2    Fixed always 0004h?   (nonzero, unlike SDIO) (RESERVED5)
 40048FAh 2    ? Can be 0004h..0007h (nonzero, unlike SDIO) (RESERVED6)
 40048FCh 2    ? Can be 0024h..00FFh?                       (RESERVED7)
 40048FEh 2    ? Can be 0024h..00FFh?   (RESERVED8 / TC6371AF:Revision)
 4004900h 2    SD_DATA32_IRQ
 4004902h 2    Fixed always zero?
 4004904h 2    SD_DATA32_BLK_LEN
 4004906h 2    Fixed always zero?
 4004908h 2    SD_DATA32_BLK_COUNT
 400490Ah 2    Fixed always zero?
 400490Ch 4    SD_DATA32_FIFO
 4004910h F0h  Fixed always zerofilled?
 ARM7 DSi SD/MMC Registers for SDIO access (for Atheros Wifi)
 4004A00h 200h SDIO_xxx (same as SD_xxx at 4004800h..40049FFh, see there)
 4004A02h 2    SDIO_CARD_PORT_SELECT (slightly different than 4004802h)
 4004AF8h 2    Fixed always zero? (unlike SD_xxx at 40048F8h) (RESERVED5)
 4004AFAh 2    Fixed always zero? (unlike SD_xxx at 40048FAh) (RESERVED6)

DSi SD/MMC I/O Ports: Command/Param/Response/Data

4004800h/4004A00h - SD_CMD - Command and Response/Data Type (R/W)

 15    undoc   Unknown/undoc  (read/write-able)
 14    undoc   Security Cmd?  (0=Normal, 1=Whatever/Security?) (sdio?)
 13    undoc   Data Length    (0=Single Block, 1=Multiple Blocks)
 12    undoc   Data Direction (0=Write, 1=Read)
 11    NTDT    Data Transfer  (0=No data, 1=With data)
 10-8  REP2-0  Response Type  (0=Auto, 1..2=Unknown/Reserved, 3=None, 4=48bit,
                               5=48bit+Busy, 6=136bit, 7=48bitOcrWithoutCRC7)
 7-6   CMD1-0  Command Type   (0=CMD, 1=ACMD, 2..3=unknown, maybe GEN WR/RD?)
 5-0   CIX     Command Index  (0..3Fh, command index)

Setting Command Type to "ACMD" is automatically sending an APP_CMD prefix prior to the command number. For Multiple Blocks, the hardware supports automatically sending STOP_TRANSMISSION after the last block.
DSi software is usually setting Response Type to "Auto", which is causing the hardware to use the correct response/data type for standard SD/MMC commands (bit11-13 are ignored/should be zero when using "Auto"; and maybe same for bit14-15?).
One exception is that the DSi firmware isn't using "Auto" for SDIO commands (maybe the hardware isn't aware of them; or it's unable to distinguish between read/write direction of CMD53, which would require examining the command's PARAM bits).
There might be subtle differences between some SD and MMC commands, unknown if/how "Auto" is working in that cases; unknown if there's a SD-or-MMC mode select bit for that purpose in some configuration register.
Invalid values can cause ILA error (particulary on setting NTDT for CMD12, or for CMD's Response=None). ILA error will also occur if an old CMD is still busy.

4004804h/4004A04h - SD_CMD_PARAM0-1 - Argument (32bit, 2 halfwords) (R/W)

 31-0  Parameter value for CMD

The parameter value should be written <before> sending the command via SD_CMD/SDIO_CMD.

400480Ch/4004A0Ch - SD_RESPONSE0-7 - Response (128bit, 8 halfwords) (R)

After sending a command, wait for the CMDRESPEND bit (IRQ_STATUS.bit0) to get set, then read the RESPONSE (if the command does have any response).

For normal 32bit responses:
 31-0      Response
 127-32    Older Responses
For CID/CSD responses:
 119-0     120bit Response
 127-120   Zero (always?)

Seems to be left-shifted when receiving response bits. So, for 32bit responses, bit0-31 would contain the current response, and bit32-127 would contain older responses.

DATA16 vs DATA32

Data can be transferred in 16bit or 32bit units (as selected in DATA_CTL.bit1 and DATA32_IRQ.bit1). There are separate data, block len, and block count registers for 16bit and 32bit mode (that's probably due to some odd patchwork, where the manufacturer has added 32bit support to the original 16bit chip design).
Naturally, a 32bit transfer is faster than two 16bit transfers. Nethertheless, the DSi firmware does use both 32bit and 16bit mode once and then; 32bit mode is required for NDMA transfers (which don't support 16bit).

40048D8h/4004AD8h - SD_DATA_CTL

 15-13  Unknown (usually 0)
 12     Unknown (usually 1)                                             (R?)
 11-6   Unknown (usually 0)
 5      Unknown (read/write-able) (usually 0)                           (R/W)
 4      Unknown (usually 1)                                             (R?)
 3-2    Unknown (usually 0)
 1      Select 16bit/32bit Data Mode (0=DATA16, 1=DATA32, see 4004900h) (R/W)
 0      Unknown (usually 0)

Known written values are 0000h and 0002h. However, known read values are 1010h and 1012h.
DATA32 mode requires setting both 40048D8h.bit1 and 4004900h.bit1. For DATA16 mode, both bits should be zero (though DATA16 seems to be also working the same way when only either of the bits is zero).

400480Ah/4004A0Ah - SD_DATA16_BLK_COUNT - "Transfer Block Count" (R/W)

4004908h/4004B08h - SD_DATA32_BLK_COUNT (R/W)

 15-0   Number of Data Blocks for multiple read/write commands (0..FFFFh)

In Data32 mode, DATA32_BLK_COUNT is decremented after each block (except after the last block, where it stays at 0001h instead of getting zero). In Data16 mode, SD_DATA16_BLK_COUNT doesn't decrease (instead, there must be some hidden internal counter register).
If enabled in STOP_INTERNAL_ACTION.bit8, then the hardware will be automatically sending STOP_TRANSMISSION (CMD12) after the last block (otherwise the decrement occurs as described above, but the hardware keeps transferring blocks infinitely).

4004826h/4004A26h - SD_DATA16_BLK_LEN - Transfer Data Length (R/W)

4004904h/4004B04h - SD_DATA32_BLK_LEN (R/W)

 15-10  Unknown/unused (appears to be always zero)
 9-0    Data Block Length in bytes (for DATA16: clipped to max 0200h by hw)

Should be usually 0200h (for 512-byte SD/MMC memory blocks). Other values may be needed for SDIO functions, or when accessing SSR/SCR/PWD registers via data transfers.
DATA32_BLK_LEN can be max 3FFh (unlike DATA16_BLK_LEN which is clipped to max=200h by hardware).

4004830h/4004A30h - SD_DATA16_FIFO - Data Port (SD_FIFO?)

400490Ch/4004B0Ch - SD_DATA32_FIFO

For Data16:
 15-0   Data (16bit) (...or could it be accessed as 32bit, too?)
For Data32:
 31-0   Data (32bit) (...or could it be accessed as 16bit, too?)

Transfer data here (read after RXRDY gets set, or write after TXRQ gets set). FIFO size is unknown (if there's any FIFO behind it).

DSi SD/MMC I/O Ports: Interrupt/Status

400481Ch/4004A1Ch - SD_IRQ_STATUS0-1 - Interrupt Status (R/ack)

4004820h/4004A20h - SD_IRQ_MASK0-1 - Interrupt Mask (R/W)

The IRQ_STATUS registers contain acknowledge-able IRQ Flags (those bits that that are maskable in IRQ_MASK register), as well as static read-only status bits without IRQ function (eg. WRPROTECT).

  • IRQ Flags/Write (0=Acknowledge, 1=No change)
  • IRQ Flags/Read (0=No IRQ, 1=IRQ)
  • IRQ Mask (0=Enable, 1=Disable) (8B7F031Dh when all IRQs disabled)
 Bit Stat  Mask  Function
 0   SREP  MREP  CMDRESPEND    (response end) (or R1b: busy end)
 1   0     0     Unknown/unused (always 0)
 2   SRWA  MRWA  DATAEND       (set after (last) data block end)
 3   SCOT  MCOT  CARD_REMOVE (0=No event, 1=Is/was newly ejected)      ;\
 4   SCIN  MCIN  CARD_INSERT (0=No event, 1=Is/was newly inserted)     ; SD
 5   undoc 0     SIGSTATE    (0=Ejected, 1=Inserted) (SDIO: always 1)  ; Slot
 6   0     0     Unknown/unused (always 0)                             ; Sw's
 7   undoc 0     WRPROTECT   (0=Locked/Ejected, 1=Unlocked/HalfEjected);/
 8   undoc undoc CARD_REMOVE_A (0=No event, 1=High-to-Low occurred)    ;\SD
 9   undoc undoc CARD_INSERT_A (0=No event, 1=Low-to-High óccurred)    ; Slot
 10  undoc 0     SIGSTATE_A    (usually 1=High) ;also as so for SDIO   ;/Data3
 11  0     0     Unknown/unused (always 0)
 12  0     0     Unknown/unused (always 0)
 13  0     0     Unknown/unused (always 0)
 14  0     0     Unknown/unused (always 0)
 15  0     0     Unknown/unused (always 0)
 16  SCIX  MCIX  CMD_IDX_ERR   Bad CMD-index in response      (RCMDE,SCMDE)
 19  SDTO  MDTO  DATATIMEOUT   Data Timeout                (NRCS,NWCS,KBSY)
 20  SFOF  MFOF  RXOVERFLOW    HOST tried write full
 21  SFUF  MFUF  TXUNDERRUN    HOST tried read empty
 22  SCTO  MCTO  CMDTIMEOUT    Response start-bit timeout         (NRS,NSR)
 23  ???   0     Unknown/undoc (usually set) (zero after sending TX data?)
 24  SBRE  MBRE  RXRDY         (fifo not empty) (request data read)
 25  SBWE  MBWE  TXRQ          (datafifoempty?) (request data write)
 26  0     0     Unknown/unused (always 0)
 27  undoc undoc Unknown/undoc  (bit27 is mask-able in IRQ_MASK)
 28  0     0     Unknown/unused (always 0)
 29  undoc 0     CMD_READY? (inverse of BUSY?) (unlike toshiba ILFSL/IFSMSK)
 30  undoc 0     CMD_BUSY
 31  ILA   IMSK  Illegal Command Access (old CMD still busy, or wrong NTDT)

Normally, IRQs should be acknowledged by writing "FLAGS=NOT X", whilst the firmware is using an unstable "FLAGS=FLAGS AND NOT X" read-modify-write function (accidentally acknowledging any IRQs that have newly occurred during that operation).

4004900h/4004B00h - SD_DATA32_IRQ

 15-13  Unknown/unused (appears to be always zero)
 12     DATA32_BUSY IRQ Enable   (0=Disable, 1=Enable)                  (R/W)
 11     DATA32_RXRDY IRQ Enable  (0=Disable, 1=Enable)                  (R/W)
 10     DATA32 Abort/Flush FIFO? (0=No change, 1=Clear Bit8,9)          (W)
 9      DATA32_BUSY IRQ Flag     (auto cleared after...)                (R)
 8      DATA32_RXRDY IRQ Flag    (auto cleared after...)                (R)
 7-2    Unknown/unused (appears to be always zero)
 1      Select 16bit/32bit Data Mode (0=DATA16, 1=DATA32, see 40048D8h) (R/W)
 0      Unknown/unused (appears to be always zero)

Can be 1A02h, but changes to 1802h after reading from somewhere (maybe from DATA32_FIFO?).
Bit8,9 are extra IRQ flags, the flags get set ONLY in DATA32 mode (not in DATA16 mode).

400482Ch/4004A2Ch - SD_ERROR_DETAIL_STATUS0-1 - Error Detail Status

This register contains extra info about the error bits in SD_IRQ_STATUS. The error bits (except bit13/always set) are automatically cleared when sending a new command by writing to SD_CMD.

 31-23 0      Unknown/unused (always zero)
 22    KBSY   Timeout for CRC status busy                          ;\STAT.19
 21    NWCS   Timeout for CRC status   (can occur for Data Write)  ; (SDTO)
 20    NRCS   Timeout for Data start-bit, or for Post Data Busy    ;/
 19-18 0      Unknown/unused (always zero)
 17    NRS    Response Timeout for auto-issued CMD12               ;\STAT.22
 16    NCR    Response Timeout for non-auto-issued CMD's           ;/(SCTO)
 15-14 0      Unknown/unused (always zero)
 13    undoc  Unknown/undoc  (always 1)                            ;-Always 1
 12    0      Unknown/unused (always zero)
 11    WCRCE  CRC error for Write CRC status for a write command   ;\
 10    RCRCE  CRC error for Read Data                              ; STAT.17
 9     SCRCE  CRC error for a Response for auto-issued CMD12       ; (SCRC)
 8     CCRCE  CRC error for a Response for non-auto-issued CMD's   ;/
 5     WEBER  End bit error for Write CRC status                   ;\
 4     REBER  End bit error for Read Data                          ; STAT.18
 3     SEBER  End bit error for Response for auto-issued CMD12     ; (SEND)
 2     CEBER  End bit error for Response for non-auto-issued CMD's ;/
 1?    SCMDE  Bad CMD-index in Response of auto-issued CMD12       ;\STAT.16
 0     RCMDE  Bad CMD-index in Response of non-auto-issued CMD's   ;/(SCIX)

Note: CMD12 is STOP_TRANSMISSION (automatically sent after BLK_COUNT blocks).
The four "auto-issued CMD12" bits exist for SD registers only (not for SDIO, going by old toshiba datasheets; which may be wrong). SCMDE is probably in bit1 (though, official specs say bit0, which would be same as RCMDE).
Some error bits can be intentionally provoked: Bit8=1 when programming the controller to expect GET_STATUS to return a 136bit response. Bit16=1 when sending GET_CID in "tran" state. Bit20=1 when sending GET_STATUS configured to expect a data/read reply. Bit21=1 when sending GET_STATUS configured to expect a data/write block (and with actually sending a data block to it).

DSi SD/MMC I/O Ports: Control Registers

4004802h/4004A02h - SD_CARD_PORT_SELECT

 15-11 Unknown/unused (appears to be always zero)
 10    Unknown (should be set on writing) (reads as zero)              (W)
 9-8   Unknown (Always 2 for SD/4004802h, always 1 for SDIO/4004A02h)  (R)
 7-4   Unknown/unused (appears to be always zero)
 3-1   Unknown                                                         (R/W)
 0     Port Select (0=SD Card Slot, 1=Onboard eMMC) (for SDIO: Unknown)(R/W)

4004828h/4004A28h - SD_CARD_OPTION - Card Option Setup

 15   undoc Bus Width (0=4bit, 1=1bit)                                   (R/W)
 14   undoc Unknown (usually set)                                        (R?)
 13-9 0     Unknown/unused (appears to be always zero)
 8    undoc Unknown (firmware tries to toggle this after CLK change?)    (W?)
 7-4  RTO   Data start/busy timout (2000h SHL 0..14, or 15=100h SDCLK's) (R/W)
 0-3  TO?   Unknown (another timeout, maybe for SDIO? in 32KHz units?)   (R/W)

Among others, this register should contain a 4bit timeout setting, "RTO[3:0] for SD (aka TO[3:0] for SDIO) timeout period for data start/busy bits, in the form of a multiple number of the SDCLK period." Unknown which "multiple numbers" that's referring to (probably some exponential/table values). Settings spotted on DSi are 40E0h,40EEh.

4004824h/4004A24h - SD_CARD_CLK_CTL Card Clock Control

 15-11 Unknown (always 0)   ;unlike Toshiba: no HCLK divider-disable in bit15)
 10    Unknown (0=Normal, 1=Unknown, doesn't affect SDCLK output?)       (R/W)
 9     Unknown (0=Normal, 1=Unknown, freezes SDCLK output?)              (R/W)
 8     SDCLK Enable (0=Force SDCLK=LOW, 1=Output SDCLK=HCLK/n)           (R/W)
 7-0   HCLK Div (0,1,2,4,8,16,32,64,128 = Div2,4,8,16,32,64,128,256,512) (R/W)

The DSi uses HCLK=33.513982 MHz, the SDCLK pin can range from HCLK/512=65kHz to HCLK/2=16.757MHz, max transfer rate would be thus 8MByte/s in 4bit mode.
Card detection should be done at a low clock rate. For SD/MMC, the DSi starts with HCLK/128, and uses the clock specified in CSD register after detection (when extracting bits from CSD: mind the different 120bit-without-CRC vs 128bit-with-CRC notations). For SDIO, the DSi starts with HCLK/256, and switches to HCLK/2 after reading SDIO Bus Speed register (Function0:00013h).
The SDCLK pins are permanently pulsed, even for devices deselected via SD_CARD_PORT_SELECT.0, and even if no CMD or DATA is being transferred. However, the DSi firmware is usually stopping SDCLK via Bit8=0 when not accessing SD/MMC (doing so may reduce noise and power consumption).
Trying to set bit9, or to set more than one bit in bit7-0 will freeze the SDCLK output (in this case SDCLK may get stuck HIGH or LOW, unlike Bit8=0 which forces LOW).

4004808h/4004A08h - SD_STOP_INTERNAL_ACTION

 15-9   Unknown/unused (appears to be always zero)
 8      Auto-Stop (1=Automatically send CMD12 after BLK_COUNT blocks)  (R/W)
 7-1    Unknown/unused (appears to be always zero)
 0      Unknown                                                        (R/W)

Stop whatever internal action for whatever purpose in whatever situation?
Existing code does set bit8 (prior to changing SD_DATA16_BLK_COUNT).
Existing code does clear bit0 (alongsides with IRQ enable/acknowlege or so).

40048E0h/4004AE0h - SD_SOFT_RESET - Software Reset

 15-3 Unknown/unused (appears to be always zero)
 2    Unknown (always 1)                                            (R?)
 1    Unknown (always 1) (though firmware tries to toggle this bit) (R?)
 0    SRST Soft Reset (0=Reset, 1=Release)                          (R/W)

Software should apply reset after sensing card insertion/removal, and (thereafter) release reset in case of card insertion. Software reset does acknowledge all IRQs (except that from SDIO /IRQ pin?), and does probably also reinitialize some other registers.
Clearing bit0 does force following settings (while and as long as Bit0=0):

 SD_RESPONSE0-7            = zerofilled
 SD_IRQ_STATUS0-1          = all IRQs flags acknowledged
 SD_ERROR_DETAIL_STATUS0-1 = all bits cleared (except bit13/always set)
 SD_CARD_CLK_CTL           = bit 8 and 10 cleared
 SD_CARD_OPTION            = 40EEh

All other registers seem to be left unaffected (including the the extra IRQ flags in 4004900h); though there may be some further hidden effects (like aborting transfers or resetting internal registers).
Note: The DSi firmware does issue reset by toggling both bit0 and bit1, although bit1 does seem to be read-only (always 1), and trying to clear that bit doesn't seem to have any effect at all.

DSi SD/MMC I/O Ports: Unknown/Unused Registers

40048F6h/4004AF6h - Firmware tests bit0 (but, always 0?) (RESERVED4)

 15-1   Unknown (0)
 0      Unknown (tested by firmware) (usually 0)       (R)

4004836h/4004A36h - SD_CARD_INTERRUPT_CONTROL ---- USED by SDIO

4004A36h is used in SDIO IRQ handler.
On DSi, this register looks as so:

 15-2   Unknown (0)
 1      Unknown (gets set automatically after 2 seconds?) (and also R/W ?)
 0      Unknown (usually always 0) (tested by firmware?)              (R?)

Whilst old toshiba datasheets specify it as so:

 15-13  ?      Unknown (zero on DSi)
 12     CINT0  SDIO Interrupt Flag (0=none/ack, 1=irq)   (/IRQ aka Data1 pin)
 11-9   ?      Unknown (zero on DSi)
 8      CIMSK0 SDIO Interrupt Mask (0=enable, 1=disable) (/IRQ aka Data1 pin)
 7-0    ?      Unknown (zero on DSi)

Acknowledge by writing CINT0=0, or CIMSK0=1 (uh, really?), or hard reset (unlike as for other SD/MMC interrupts, soft reset does not acknowlege this interrupt type?).

4004838h/4004A38h - SDCTL_CLK_AND_WAIT_CTL ---- USED by SDIO

4004A38h is used in SDIO IRQ handler.
On DSi, this register looks as so (usually zero):

 15-14  Unknown (usually 0)                            (R/W)
 13-3   Unknown (0)
 2-0    Unknown (usually 0)                            (R/W)

Whilst old toshiba datasheets specify it as so:

 15-0   Unknown (bit8 should be set after SD_CARD_CLK_CTL change?)

Below registers don't seem to be used by existing software...

4004834h/4004A34h - SD_TRANSACTION_CTL - Transaction Control

 15-10 Unknown/unused (appears to be always zero)
 9-8   Unknown                                     (R/W)
 7-3   Unknown/unused (appears to be always zero)
 2     Unknown                                     (R/W)
 1     Unknown/unused (appears to be always zero)
 0     Unknown                                     (R/W)

40048F2h/4004AF2h - Can be 0003h

 15-2   Unknown (0)
 1-0    Unknown (0..3)                                 (R/W)

40048F4h/4004AF4h - Can be 0770h

 15-11  Unknown (0)
 10-8   Unknown (0..7)                                 (R/W)
 7      Unknown (0)
 6-4    Unknown (0..7)                                 (R/W)
 3-0    Unknown (0)

40048FAh - Can be 0007h (nonzero, unlike SDIO) (RESERVED6)

 15-3   Unknown (0)
 2      Unknown (1=normal, 0=data/read from card to fifo busy?)       (R)
 1-0    Unknown (0..3)                                 (R/W? or rather R?)

40048FCh/4004AFCh - Can be 0024h..00FFh? (RESERVED7)

40048FEh/4004AFEh - Can be 0024h..00FFh? (RESERVED8 / TC6371AF:Revision)

 15-8   Unknown (0)
 7-0    Can be 24h..FFh       parts (R) and parts (R/W)?

Unused Registers with Fixed value (all bits read-only, or write-only)

 400482Ah/4004A2Ah 2    Fixed always zero?
 4004832h/4004A32h 2    Fixed always zero?   ;(TC6371AF:BUF1 Data MSBs?)
 400483Ah/4004A3Ah 2    Fixed always zero?   ;(SDCTL_SDIO_HOST_INFORMATION)
 400483Ch/4004A3Ch 2    Fixed always zero?   ;(SDCTL_ERROR_CONTROL)
 400483Eh/4004A3Eh 2    Fixed always zero?   ;(TC6387XB: LED_CONTROL)
 4004840h/4004A40h 2    Fixed always 003Fh?
 4004842h/4004A42h 2    Fixed always 002Ah?
 4004844h/4004A44h 6Eh  Fixed always zerofilled?
 40048B2h/4004AB2h 2    Fixed always FFFFh?
 40048B4h/4004AB4h 6    Fixed always zerofilled?
 40048BAh/4004ABAh 2    Fixed always 0200h?
 40048BCh/4004ABCh 1Ch  Fixed always zerofilled?
 40048DAh/4004ADAh 6    Fixed always zerofilled?
 40048E2h/4004AE2h 2    Fixed always 0009h?  ;(RESERVED2/9, TC6371AF:CORE_REV)
 40048E4h/4004AE4h 2    Fixed always zero?
 40048E6h/4004AE6h 2    Fixed always zero?   ;(RESERVED3, TC6371AF:BUF_ADR)
 40048E8h/4004AE8h 2    Fixed always zero?   ;(TC6371AF:Resp_Header)
 40048EAh/4004AEAh 6    Fixed always zerofilled?
 40048F0h/4004AF0h 2    Fixed always zero?   ;(RESERVED10)
 40048F8h          2    Fixed always 0004h?   (unlike SDIO) (RESERVED5)
 4004AF8h          2    Fixed always zero?    (unlike SD)   (RESERVED5)
 4004AFAh          2    Fixed always zero?    (unlike SD)   (RESERVED6)
 4004902h/4004B02h 2    Fixed always zero?
 4004906h/4004B06h 2    Fixed always zero?
 400490Ah/4004B0Ah 2    Fixed always zero?
 4004910h/4004B10h F0h  Fixed always zerofilled?