SoM-A5D36 User Manual
Revision 1.30 © 2015
- 8 -
2.4.1
External Bus
The SoM-A5D36 provides a flexible external bus for connecting peripherals. The CPLD of the SoM-200GS
and SoM-250GS connect through a subset of these connections. The WKUP pin has a Maximum input
voltage of 3.3V (pulled up on-module to 3.3V) and Shutdown has a maximum output voltage of 3.3V. The
Flash WP for the Serial Flash is active-low and pulled up on-module.
Table 1: External Bus Interface
SODIMM
Pin#
SoM
Pin Name
Processor
Pin Name(s)
Port Line
Description
145
GP_CSA
NCS1
PE27
General Purpose Chip Select CS0
146
GP_CSB
NCS2
PE28
General Purpose Chip Select CS4
147
GP_CSC
NCS3
N/A
General Purpose Chip Select CS2
148
GP_CSD/Shutdown
PWRDN
N/A
Processor Shutdown Output
149
WR
NWE
N/A
Write Signal
150
RD
NRD
N/A
Read Signal
151
RST_IN
NRST
*
Processor Reset
152
RST_OUT
~RST_OUT
*
Processor Reset
153
WAIT
NWAIT
PE30
Shutdown Control
154
~FLASH WP
*
*
Serial Flash Write Protect
54
WAKEUP
WKUP
N/A
Processor Wakeup Input
157
BOOT_OPTION0
BMS
N/A
Boot0 Option Select
158
BOOT_OPTION1
*
*
Boot1 Option Select
175-193
A0
–
A18
A0
–
A18
PE0-PE18
Address Bus
194
A19
A19
PE19
Address Bus line A19
195
A20
A20
PE20
Address Bus line A20
196
A21
A21
PE21
Address Bus line A23
159-174
D0 - D15
D0
–
D15
N/A
Data Bus
*The RST_IN pin is an active low input that drives the processor reset pin. The RST_OUT pin is an active
low output that is driven low by either the watchdog timer or a software reset. The ~FLASH_WP pin is an
active low input that prevents the serial NOR flash from being written to. The BOOT_OPTION1 pin is an
input that disables the serial NOR flash.
