You can download firmware using a flash card or using a network connection, but I prefer the flash card, especially when the network is something tricky like DH485.
PanelView Standard terminals with v3 or later firmware support ordinary "ATA" style memory cards. While RA will only officially support their cards because they're tested for compatability, I've had very good success using ordinary SanDisk CompactFlash cards in a PCMCIA carrier module.
The PanelViews only understand the classic FAT formatting style, so the CF card needs to be formatted for FAT, not FAT32 or NTFS or anything else. Usually that means a card under 2 GB.
You will find that the firmware is contained in a directory of files "to be used over a network" and a directory of files "to be used with a flash card".