Design-In - Electrical Aspects
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COMX Communication Modules | Design Guide
DOC100901DG18EN | Revision 18 | English | 2013-12 | Released | Public
© Hilscher, 2002-2013
3.1.7
Common Signals of the Host Interface
3.1.7.1
Power Supply of the COMX Modules
Only a single 3.3 V operation voltage is needed for the COMX Module. The voltage must be regu-
lated and can have a tolerance of ±5% (3.135 ... 3.465 V) and must be connected twice to the sys-
tem bus connector X1. To avoid EMI problems we suggest using bypass capacitors in the power
supply path. All other special voltages required on the COMX Module are generated by on board
DC/DC converter.
A watchdog circuit on all COMX Modules supervises the voltage and the microprocessor. If the
voltage decreases below the voltage reset level of typically 2.93 V (2.85 ... 3.00 V) the COMX
Module are hold in reset state. If the voltage exceeds the reset voltage threshold the COMX Mod-
ule will begin with the power up sequence. To avoid problems with the power supply we
recommend using a voltage of 3.3 V. So the operation will be in the safe range of voltage operation
area and short voltage drops, spikes and noise will not cause any reset conditions.
The maximum current depends on netJACK module type. For specific current values see section
Technical Data on page 67.
3.1.7.2
RESET Signal
It is possible to reset the COMX Module by the extra reset signal DPM_RESETn. For operation of
the COMX Module it is important to switch the signal DPM_RESETn to high level. Then the COMX
Module begins with the program execution and initialization. This power up time is different for
each COMX Module. Normally, the time is about less than two seconds. The COMX Module is in
reset state when the signal DPM_RESETn has a static low level. To reset the COMX Module the
DPM_RESETn signal must be low for more than 10 µs.
Note
During Reset all signals of the dual-port memory are configured as inputs! The output
level could be floating. If the host system needs a stable level a pull-up or pull-down re-
sistor is required on the host board. The COMX has pull-up resistors on board for the
output lines DPM_BUSYn and DPM_DIRQn.
3.1.8
Signals of the Host Interface – Parallel Dual-Port Memory Mode
3.1.8.1
The Dual-Port Memory Bus of COMX
The communication for all input and output data and control commands between the COMX and
the host system are exchanged over the dual-port memory. The communication is not compatible
to the COM-A/-B-/C devices. The address map of the dual-port memory is different.
From host system side, the dual-port memory looks like static RAM. The dual-port memory size of
the COMX module depends on the COMX module type, see section
Dual-Port Memory Sizes and Modes
on page 39. Only a few signals are used to control the access
to the dual-port memory.
The maximum driving capability for the data lines is 8 mA (COMX 50, COMX 100) respectively
6 mA (COMX 10) and 9 mA (COMX 51).
To avoid data loss through simultaneous access at the same memory cell, it is necessary to use
the DPM_BUSYn signal. See section
Please refer to the special documents for the basic description of the data model and communica-
tion methods with devices based on the netX.
