16.2 MMC Functions standard CPUs16.2.1 SFC 220 ... 222 - MMC AccessBy means of these blocks there is the possibility to integrate MMC access to your applica-tion program. Here a new file may be created respectively an existing file may be openedfor accessed when a MMC is plugged-in. As long as you do not open another file, youmay access this file via read/write commands.For deploying the SFCs 220, 221 and 222, you have to regard the following restrictions:n A read res. write access to the MMC is only possible after creation res. opening of thefile via SFC 220.n The data on MMC must not be fragmented, for only complete data blocks may beread res. written.n When transferring data to the MMC from an external reading device, they may befragmented, i.e. the data is divided into blocks. This may be avoided by formatting theMMC before the write access.n At a write access from the CPU to the MMC, the data is always stored not frag-mented.n When opening an already existing file, you have to use the same FILENAME andFILESIZE that you used at creation of this file.n A MMC is structured into sectors. Every sector has a size of 512byte. Sector overlap-ping writing or reading is not possible. Access to sector overlapping data is only pos-sible by using a write res. read command for every sector. By giving the offset, youdefine the according sector.The following picture shows the usage of the single SFCs and their variables:For read and write accesses to the MMC, you firstly have to open the filewith SFC 220!16.2.2 SFC 220 - MMC_CR_F - create or open MMC fileBy means of this SFC a new file may be created respectively an existing file may beopened for accessed when a MMC is plugged-in. As long as you do not open another file,you may access this file via read/write commands. For more detailed information to thisand to the restrictionsÄ Chap. 16.2.1 ‘SFC 220 ... 222 - MMC Access’ page 906.OverviewRestrictionsOverviewVIPA SPEED7System BlocksMMC Functions standard CPUs > SFC 220 - MMC_CR_F - create or open MMC fileHB00 | OPL_SP7 | Operation list | en | 18-30906
