Propox MMstR75xFR, User Manual

Page: 7 / 14

7
Memory is available directly on minimodule pins:
P0.04 – DF_CS Chip Select
P0.05 Clock Input
P0.06 Data Input
P0.07 Data Output
Pin chip select is also connect to microcontroller ports by 0
Ω
resistor and it can by directly use
without outside connections.
It should be kept in mind that if Serial Flash memory is installed, the just outlined port terminals
cannot be used externally to the module. Of course the SPI bus can be used for
communication with external peripherals, under the condition that they will have circuit
selection inputs (CS).
A detailed description of Serial Flash circuits is on the STMicroelectronics page:
www.st.com .
RESET circuit RESET circuit RESET circuit RESET circuit
The MMstr75xFR has a built-in voltage monitoring circuit built around the DS1818 integrated
circuit. The circuit generates a RESET signal in case when the supply voltage value is lower
than 3V. This takes place when the supply voltage is switched on or off, when the VCC voltage
changes its value from 0 to 3.3 V. The guard circuit detects also momentary VCC voltage
drops. A short duration drop of VCC below 3V causes the generation of a resetting signal of
100 ms duration. This signal is applied directly to the resetting input of the microcontroller and
is led out to a module connector and it can be used as the zeroing output resetting external
circuits and as the input for resetting the module, e.g. by means of the RESET button. In such
a case the RESET button can short the RESET line directly to ground. An implementation of
the reset circuit is presented in the diagram below.
Figure 4 RESET circuit implementation