Cypress Semiconductor CY8C21534 Specifikace stáhnout pdf (Strana 36)

continuous write command, the host device must fill the remaining space of the last

sector with dummy bytes of the hex value 0x00 and then send the stop token in

order to receive a data accepted token from the SD card. The stop token is a single

byte of hex 0xFD.

After the stop token is sent and the data has been correctly written to the SD card

memory, the MCU will cut power to the WiFly wireless unit and send a signal back to

the Control MCU that the file has been successfully written to the card and it is ready

for viewing. When all sectors have been properly written, the digital photo frame can

read the file as a normal picture file.

The locations of the entries on the SD card can vary with cards. The SD card utilized

for this project is a Transcend 2GB Micro SD card. This card uses 64 sectors per cluster

of memory. This gives a total of 32768 bytes of memory per cluster. For this project

the FAT entries were written to include the space of 10 clusters for the file. This gives

a usable memory space of 327680 bytes for the file. The Directory entry includes

the card information, file name, size, starting sector, time, and date information. The

array in the MCU only includes enough information to cover the card information and

the information for one file. The file name, date of creation, starting memory sector,

and other aspects of the file can remain the same every time. The only information

changed is the file size. The last entry made is the volume entry where the raw data is

written to. The beginning sector for the raw data is always set to sector 512, and the

reserved space continues for the next 327680 bytes.

No system settings of the digital photo frame have been changed from the default

values. The circuit board of the unit has been enclosed and the buttons and card slots

have become inaccessible, as they are no longer needed for the operation of the

schedule.

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Cypress Semiconductor CY8C21534 Specifikace Strana 36