The DMP3250di is basically the same as the DMP3160, but with Dual Interface (as indicated by the "di" suffix) (with additional RS232 connector). Aside from the suffix, Amstrad did (for whatever reason) also change the model number from 3160 to 3250 - although the technical specs seem to be more less unchanged. Namely, like the DMP3160, the DMP3250di supports only 160 chars/second (not 250).
Some details that are different: Additional RS232 hardware (not a major change, since older DMP2000-3160 mainboards & firmwares did already have provisions for RS232 daugtherboards, too). The case needs a new opening for the RS232 connector. Another small difference is that the metal stands are arranged differently (the DMP3160 and older models had their "feet" on left & right side, the DMP3250di has them at front & rear side). And, the transparent plastic cover is bigger (resembles more the CPC-style DMP2000/DMP2160 models than the PC/PCW-style DMP3000/DMP3160 ones).
The printer is mainly intended for use with PC/PCWs, the gray color is't matched to the design of the CPC, and the RS232 input would be fairly useless for CPCs (except as an overcomplicated way for bypassing the CPC's 7bit Printer Port limit).
For (detailed) general information about Amstrad/Scheider printers, see:
- Amstrad/Schneider Printer Models
- Amstrad/Schneider Printer Technical Specifications
- Amstrad/Schneider Printer Control Codes
- Amstrad/Schneider Printer Support for 7bit Printer Ports
- Amstrad/Schneider Printer Character Sets
- Amstrad/Schneider Printer Buttons and DIP Switches
- Amstrad/Schneider Printer Resources (User and Service Manuals, Datasheets, ROM-images)
- DMP3000/3160/3250di User Manual (English) (DMP3000/3160 manual from 1986) (plus preface with notes for CPC users from 1990) (unlike the French version, it doesn't include info on DMP3250di's RS232 DIP switches)
- Amstrad DMP3000/3160/3250di User Manual (French) (basically a DMP3000/DMP3160 manual - with some brief notes on the DMP3250di in the preface)
- DMP4000 and DMP3250di Leaflet (English)
- DMP3160/DMP3250di/DMP4000/LQ3500/LQ3500di/LQ5000di AMSTPRINT Leaflet (Norwegian)