Hardware 3.10.3 Data memory Data in this context comprises all operands (inputs and outputs, bit markers, byte marker, timers and counters). The monitor program also falls back on some parts of this me- mory for internal purposes. 8 kbyte of the NV-RAM described in chapter 3.10.4 are reserved for no-voltage protected operands (also called remanent operands). The volatile (non-remanent) operands are stored in a 24 kbyte S-RAM. This type of memory is cleared when the de- vice is being initialised to ensure that all memory cells have a defined status (0). Inputs and output (Ixx.xx and Oxx.xx) as well as 40 markers (M00.00...M02.07) are mapped onto the micro- processor’s so-called on-chip RAM.
These addresses can be accessed particularly fast ( а 3.10.5). 3.10.4 NV-RAM: special features NV-RAM technology (non-volatile RAM) ensures that pro- grams and data are stored safely without the use of exter- nal energy (accumulator or battery) even if you disconnect the device from the mains. They’re stored without any limi- tation in time no matter how long the device remains swit- ched off for. They resume their previous status when you restart the controller. 33