Section 3: Interface Specifications
| | RS232C SERIAL INTERFACE SIGNALS |
PIN | DIRECTION | SIGNAL DEFINITION |
20 | To Host | DTR (Data Terminally Ready) - This signal applies to Ready/Busy flow control. |
| | The printer is ready to receive data when this pin is high. It goes low when the |
| | printer is off-line, either manually or due to an error condition, and while |
| | printing in the single job buffer mode. It will also go low when the data in the |
| | buffer reaches the buffer near full level. |
CABLE REQUIREMENTS
DB9 | DB25 | HOST | INTERCONNECTION | DB25 | PRINTER |
1 | 1 | FG | < | ---------------- | 1 | FG (Frame Ground) |
2 | 3 | RD | ---------------- | > | 2 | TD (Transmit Data) |
3 | 2 | TD | <--------------- | > | 3 | RD (Receive Data) |
8 | 5 | CTS | | I-------- | 4 | RTS (Request to Send) |
| | | | I | | |
7 | 4 | RTS | | 5 | CTS (Clear to Send) |
4 | 20 | DTR | < | I-------- | 6 | DSR (Data Set Ready) |
6 | 6 | DSR* | 20 | DTR (Data Terminal Ready) |
5 | 7 | SG | <--------------- | > | 7 | SG (Signal Ground) |
* This connection at the host side of the interface would depend upon the pin that is being used as the Ready/Busy signal by the driving software. Typically, on a PC, it would be either CTS (pin5) or DSR (pin 6) on a DB-25 connector.
READY/BUSY FLOW CONTROL
Ready/Busy is the hardware flow control method for the serial interface on the M-84PRO printers. By raising/lowering the voltage level on Pin 20 of the RS232C port, the printer notifies the host when it is ready to receive data. Pin 4 (RTS) and pin 20 (DTR) are the important signals on the printer for this method of flow control. The host must be capable of supporting this flow control method for it to function properly.
X-ON/X-OFF FLOW CONTROL
X-On/X-Off flow control is used whenever hardware (Ready/Busy) flow control is not available or desirable. Instead of a voltage going high/low at pin 20, control characters representing ìPrinter Readyî (X-On =11 hexadecimal) or “Printer Busy” (X-Off = 13 hexadecimal) are transmitted by the printer on pin 2 (Transmit Data) to the host. In order for this method of flow control to function correctly, the host must be capable of supporting it. X-On/X-Off operates in a manner similar to the function of pin 20 (DTR) as previously explained. When the printer is first powered on it sends an X-Off when the “Buffer Near Full” level is reached and a X-On when the data level of the buffer drops below the “Buffer Available” mark. When the printer is taken off-line manually, it transmits an X-Off indicating it cannot accept data. When it is placed back on line manually, it sends an X- On, indicating it is again available for receipt of data. If an error occurs during printing (paper out, ribbon out), the printer sends an X-Off as soon as an error condition is detected. When the error is cleared and the printer is placed back on-line, it transmits an X-On indicating it is again ready to accept data. Upon power up if no error conditions are present, the printer will continually send X-On characters at five millisecond intervals until it receives a transmission from the host.
M84Pro Service Manual | PN: 9001113A | Page 3-5 |
