Digi does not publicly release full schematics, but similar OEM versions are available from:
Digi SM320 bootloader v1.2 DRAM: 64 MB Flash: 16 MB Cellular module: Sierra MC8775 digi sm320 service manual
Would you like help with , pinout details , or troubleshooting a specific issue on your SM320 instead? That I can guide you through directly. Digi does not publicly release full schematics, but