PURPOSE: To write the mode setting state of a printer when abnormality occurs by previously giving dump state and termination positions corresponding to the range of an abnormal part at the time of actual printing in a printer by means of a command.

CONSTITUTION: When a hexa-dump device receives printing data, it analyzes received data and judges whether it is the command of a line-starting system or not. When it is 'YES', the count value of a count buffer in the line-starting system in RAM 4 is updated. Then, received data is converted into a hexa-code and is dump-outputted. The count value of the command of the line-starting system is judged to have reached a value corresponding to the dump termination position which is previously set and which is stored in the buffer of RAM 4 of not. When it is 'NO', a system returns to the reception of received printing data at a dump mode and the above operation is repeated until the count value of the command in the line-starting system reaches the value corresponding to the dump termination position so as to continue dump output. When it is 'YES', the dump mode is released and dump output is stopped. Thus, only the part corresponding to the range of the abnormal part in actual printing is dump-outputted.