NEC PX-50VP1A 42PD2/50PD1 - Page 53

Communication Parameters (1) Communication system (2) Interface (3) Baud rate (4) Data length (5) Parity (6) Stop bit (7) Communication code Asynchronous RS-232C 9600 bps 8 bits Odd 1 bit Hex Communication Format 8bit 8bit 8bit 8bit 8bit 8bit 8bit 8bit Data length Command 2 UNIT ID 2 UNIT ID 1 Command 1 Check Sum Data Command 1 Together with Command 2, this is a number that distinguishes the various commands. For ACK, when bit 2 and bit 3 are both "1", reception of a supported command or data is indicated. When bit 2 is "0", reception of an unsupported command or data is indicated. Bit 0 and bit 1 should be set as described below. bit0 bit1 0 0 When multiple screens are selected 0 1 Not used 1 0 At time of set ID selection 1 1 At time of regular use Unit ID 1 and Unit ID 2 1) Unit ID1: Sets a number corresponding to the various sets ID (1 through 4) when multiple screens are selected, and to 1 through 256 at the time of set ID selection. "00H" must be output when the ID is not set. 2) Unit ID2: Makes settings on the occasion of simultaneously operating all sets connected in cascade at the time of multiple screen mode and at the time of set ID selection. Selection of all sets: FFH At time of regular setting: 00H Check Sum (CKS), Error Processing, and ACK 1) Checks for receive data incorporate both the following checksum and RS-232C (odd) parity. The checksum comprises the following aspects of one transmitted or received frame: Command 1, Unit 1 and 2, Command 2, data length, and the lower order 8 bits of the total data. Check Sum Example 9FH 40H Command 1 Unit ID 4FH Command 2 01H Data Length 01H 30H Data Check Sum v Total 130H 2) Error Processing (1) When the communications interval is 4 ms or greater, the arrival of a subsequent Command 1 will be recognized. If meaningful data cannot be discerned at this time, that data will not be recognized. (2) When the receive data error, checksum error, and the receive data could not all be taken in, ACK is not returned. 3) Returning an ACK When command processing exceeds 0.5 seconds following command reception, an ACK1 for which bit 3 of Command 1 has been set to "0" (during command processing) is returned every 0.5 seconds until command processing is completed. When command processing is completed, an ACK2 for which bit 3 of Command 1 has been set to "1" (at the end of command processing) is returned every 0.5 seconds until command processing is completed. Bit 1 of Command 1 is set to 0 ; when the UA2 setting is FFH, it becomes possible to simultaneously operate all sets connected in cascade and as a result, ACK is not returned. Communications Flow Plasma display Personal computer PC or other external equipment Various commands Command 2 Together with Command 1, this is a number that distinguishes the various commands. ACK When various commands are sent from a personal computer (PC) or other external equipment, the display is always ready to receive them. Note that resending of the command is recommended when an ACK is not returned from the display within 1.5 seconds. 53