Bit
Bit
Number
Mnemonic Description
Block Length LSB
Refer to Table 220 for byte description
7-0
BLEN7:0
Reset Value = 0000 0000b
Table 225. MMSTA Register
MMSTA (1.B5h Read Only) – MMC Status Register
7
6
5
4
3
2
1
0
SDWP
CDET
CBUSY
CRC16S
DATFS
CRC7S
WFRS
HFRS
Bit
Bit
Number
Mnemonic Description
SD Card Write Protect Bit
7
6
5
SDWP
CDET
Set by hardware when the SD card socket WP switch is opened.
Cleared by hardware when the SD card socket WP switch is closed.
Card Detection Bit
Set by hardware when the SD card socket presence switch is opened.
Cleared by hardware when the SD card socket presence switch is closed.
Card Busy Flag
CBUSY
Set by hardware when the card sends a busy state on the data line.
Cleared by hardware when the card no more sends a busy state on the data line.
CRC16 Status Bit
Transmission mode
Set by hardware when the token response reports a bad CRC.
Cleared by software by setting DCR bit in MMCON2.
Reception mode
Set by hardware when the CRC16 received in the data block is not correct.
Cleared by software by setting DCR bit in MMCON2.
4
3
CRC16S
Data Format Status Bit
Transmission mode
Set by hardware when the format of the token response is correct.
Cleared by hardware when the format of the token response is not correct.
Reception mode
DATFS
Set by hardware when the format of the frame is correct.
Cleared by hardware when the format of the frame is not correct.
CRC7 Status Bit
Set by hardware when the CRC7 computed in the response is correct.
Cleared by hardware when the CRC7 computed in the response is not correct.
2
1
0
CRC7S
WFRS
HFRS
This bit is not relevant when CRCDIS is set.
Whole FIFO Ready Status Bit
Set by hardware when 16 bytes can be read in receive mode or written in
transmit mode.
Cleared by hardware when FIFO is not ready.
Half FIFO Ready Status Bit
Set by hardware when 8 bytes can be read in receive mode or written in transmit
mode.
Cleared by hardware when FIFO is not ready.
Reset Value = XX00 0000b, depends wether a card is present in the socket or not and if
it is locked or not.
204
AT85C51SND3Bx
7632A–MP3–03/06
ATMEL [ ATMEL ]
