SoM-A5D36 User Manual
Revision 1.30 © 2015
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2.2
Real-Time Clock
The SoM-A5D36 has an embedded Real-time Clock. Battery backup is provided from the carrier board
using the VSTBY pin. The SoM-A5D36 will retain the RTT value register during reset and hence use it as an
RTC. The RTC has the provision to set alarms that can interrupt the processor. For example, the processor
can be placed in sleep mode and then later awakened using the alarm function.
2.3
Watchdog Timer
The SoM-A5D36 provides an external Watchdog Timer/ Supervisor (MAX6747) with an extended
watchdog timeout period of 1.42 seconds (±10%). Upon power-up the Watchdog is disabled and does not
require pulsing. To start the Watchdog, it must first be enabled. This is done by configuring port line PD8
as an output and setting it low in software. Once enabled, the Watchdog should be pulsed, using port line
PD6, continually every 1.28 seconds or faster to prevent the Watchdog from timing out and resetting the
module. If you are using the watchdog to force a system reset, you may need up to 1.56 seconds of
inactivity before the Watchdog reset will occur. The watchdog is automatically disabled upon reset but it
can also be disabled by setting PD8 high.
2.4
External Connections
The SoM-A5D36 connects to a carrier board containing its connectors, power supply and any expansion
IO, through a standard ENIG-plated (Electroless Nickel Immersion Gold) SODIMM 200-pin connection
shown below.
The SoM model will fit in any standard 200-pin SODIMM socket. These connections are designed to be
compatible with all EMAC 200-pin SoM products. See EMAC SoM 200-pin SODIMM Pinout Specification
to see how other 200-pin SoM pinouts line up with the SoM-
A5D36’s pinout.
The use of the DDR SODIMM form-
factor for EMAC’s SoMs is a sound choice that has been proven rugged
and reliable in the laptop and embedded SBC markets.
The remainder of this section describes the pinout as it applies specifically to the SoM-A5D36 processor.
