Communication system via cascade connection and communication device

A communication device on a first cascade level of a cascade connection that connects a plurality of communication devices, comprising:

• a communication control portion which holds serial communication with one of the plurality of communication devices that is on a cascade level next to the communication device;
• a buffer portion which comprises a transmission buffer and a reception buffer;
• a processing portion;
• and
• a data conversion portion,
• wherein the processing portion is configured to:
• create information destined to one of the plurality of communication devices that is n cascade levels down from the processing portion, a count of remaining cascade levels till the n-th cascade level, and an error detection code for communication data, which comprises the information destined to the communication device n cascade levels down from the processing portion and the remaining cascade level count;
• keep the communication data and the created error detection code in the transmission buffer;
• and
• execute given processing for information from the communication device n cascade levels down which is kept in the reception buffer, and
• wherein the data conversion portion is configured to:
• convert the communication data and the error detection code that are kept in the transmission buffer into serial data;
• transmit the serial data obtained by the conversion to the communication device on the next cascade level via the communication control portion;
• convert serial data that is received from the communication device on the next cascade level via the communication control portion into parallel data;
• and
• keep the parallel data obtained by the conversion in the reception buffer.

A communication device on a cascade level that is other than a first cascade level of a cascade connection that connects a plurality of communication devices, comprising:

• a communication control portion which holds serial communication between one of the plurality of communication devices that is on a preceding cascade level and one of the plurality of communication devices that is on a next cascade level;
• a buffer portion which comprises a transmission buffer and a reception buffer;
• a processing portion;
• a first data conversion portion;
• and
• a second data conversion portion,
• wherein the processing portion is configured to:
• create an error detection code for communication data that is received from the communication device on the preceding cascade level along with another error detection code;
• compare the created error detection code against the received error detection code;
• determine, when the error detection codes match, whether or not the processing portion is a transmission destination of information destined to one of the plurality of communication devices that is m cascade levels down from the communication device on the preceding cascade level, based on a remaining cascade level count which is included in the communication data along with the information and which indicates a count of remaining cascade levels till the m-th cascade level;
• create, when the information is not destined to the processing portion, new communication data in which the remaining cascade level count is reduced by 1 and newly create an error detection code for the new communication data;
• keep the created error detection code along with the new communication data in the transmission buffer;
• and
• keep, when information from the communication device m cascade levels down is received, the received information in the reception buffer,
• wherein the first data conversion portion is configured to:
• convert the communication data and the error detection code that are kept in the transmission buffer into serial data;
• transmit the serial data obtained by the conversion to the communication device on the next cascade level via the communication control portion;
• convert serial data that is received from the communication device on the next cascade level via the communication control portion into parallel data;
• and
• keep the parallel data obtained by the conversion in the reception buffer, and
• wherein the second data conversion portion is configured to:
• convert parallel data that is received from the communication device on the next cascade level and kept in the reception buffer into serial data;
• and
• transmit the serial data obtained by the conversion to the communication device on the preceding cascade level via the communication control portion.