A/C-6 (RO)
Appendix I: Interface Specifications
A/C-6 (RO) provides both a DB25 serial interface and a DB25 Centronics parallel interface.
I.1 Asynchronous Serial Communication
If you are connecting A/C-6 (RO) to a serial printer/output device, it will be transferring data asynchronously. If you are unfamiliar with asynchronous serial communication techniques, the following information may be of help to you. Some fundamental data-communications terms are defined as they relate to how A/C-6 (RO) will communicate with your printout device.
F LOW -C ONTROL S IGNALING
Flow control signaling is a way to pace the data transfer between devices of different speeds. More than just data-transfer speed is of concern when transferring data to a mechanical device such as a printer, because paper movement and other mechanical activity take time, during which the device may be unable to accept data.
Flow control signaling is used to interrupt data transfer temporarily for conditions that will automatically clear. Lost data is the most common symptom of incorrect configuration of flow control signaling.
A/C-6 (RO) supports XON/XOFF and Busy signaling for printer flow control.
When the printer is no longer able to accept incoming data, it sends an
XOFF code (13H) to A/C-6 (RO) or drops its Busy signal. A/C-6 (RO) stops output data transfer immediately. A/C-6 (RO) then waits until an XON
(11H) is received or the printer’s Busy signal is raised before sending additional data.
For a serial interface, A/C-6 (RO) can be configured to recognize the Busy signal on Pin 11 or Pin 20/6 (Pin 20 if A/C-6 (RO) is set for DCE and Pin 6 if
A/C-6 (RO) is set for DTE). When the Busy signal pin is HIGH it indicates
NOT BUSY, and when it is LOW it indicates BUSY. The NONE option is used if your printer has no means of signaling Busy. Be aware that if the NONE option is chosen and your printer goes BUSY, lost data will result.
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A/C-6 (RO)
In DCE mode:
In DTE mode:
Pin 11 HIGH=Not Busy
LOW=Busy
Pin 20 (DTR) HIGH=Not Busy
LOW=Busy
Pin 11 HIGH=Not Busy
LOW=Busy
Pin 6 (DSR) HIGH=Not Busy
LOW=Busy
XON/XOFF is a method of indicating Busy that uses characters transmitted from the receiving device back to the transmitting device. XON/XOFF is always supported by A/C-6 (RO), and is not configured.
R
EADY
S
IGNALING
Ready signaling is used to indicate the current permanent ability or inability of a device to accept data transfer. It generally reflects operator controllable device conditions. Not Ready is signaled when the printer is taken off-line, runs out of paper, or has some other fault that requires operator intervention.
When a device is Not Ready, it cannot accept data transfer.
When the printer goes Not Ready, it drops its Ready signal. A/C-6 (RO) stops data transfer immediately, and then begins a series of timed notification actions noted below. When the Ready signal is raised by the printer, A/C-6
(RO) resets itself and may resume data transfer.
For a serial interface, A/C-6 (RO) can be configured to recognize the
Ready signal on Pin 4 or 5 (DCE or DTE interface) or Pin 20 or 6 (DCE or
DTE). When the Ready signal pin is HIGH it indicates READY, and when it is
LOW it indicates NOT READY. The NONE option is used if your printer provides no means of Ready signaling. Be aware that if the NONE option is chosen and your printer goes NOT READY, lost data will result.
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A/C-6 (RO)
In DCE mode:
In DTE mode:
Pin 4 (RTS) HIGH=Ready
LOW=Not Ready
Pin 20 (DTR) HIGH=Ready
LOW=Not Ready
Pin 5 (CTS) HIGH=Ready
LOW=Not Ready
Pin 6 (DSR) HIGH=Ready
LOW=Not Ready
If a Not Ready condition is detected, the READY indicator goes off, and
ERROR 01 is displayed. A/C-6 (RO) then initiates a configurable error delay timeout. What happens next is determined by the settings of two configuration options. The following description is written assuming that options PRINTER ERROR TIMEOUT and AUTO-HOLD PRINT are set to their defaults (PRINTER ERROR TIMEOUT=EMULATE 3287 and AUTO-
HOLD PRINT=NONE).
Upon detection of the Not Ready condition, A/C-6 (RO) allows one minute for the operator to either fix the printer, or press the Hold Print button, before an Intervention Required is sent to the host. ERROR 31 is displayed.
If Hold Print is pressed within the first minute, however, more time (10 minutes) is allowed before Intervention Required is sent. If 10 minutes elapses and the printer is still Not Ready, ERROR 08 is displayed. In all cases,
A/C-6 (RO) will only send Intervention Required to the host when a print operation is taking place, and if PRINTER ERROR PRESENTATION is configured to EMULATE the IBM 3287.
DCE/DTE
All serial interface equipment can be classified as either Data
Communications Equipment (DCE) or Data Terminal Equipment (DTE).
Modems (used in a pair with a phone-line connection) and line drivers are examples of DCE. Most terminals and output devices (such as serial printers) are classified as DTE.
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