AMT Datasouth 41AY89AR777 - Manual (Page 53)

Table 3.1 Serial Interface Connector-Pin Assignment
PIN ASSIGNMENT
1 Chassis Ground
2 Serial Data Out Asynchronous output data line
3 Serial Data In Asynciironous input data line
7 Signal Ground
11 Data Terminal Ready
(DTR)
20 Data Terminal Ready
(DTR)
indicates the printer is open for
communication and can accept or transmit
data
3.3 PARALLEL INTERFACE
The printer features a TTL level 8-bit parallel interface which can be accessed
through the 36-pin female connector on the back of the printer (see Figure 1.2).
The parallel interface provides the user with a simple, high speed interface for
communications with a CPU or host system. Operating with parallel data in lieu
of serial offers several advantages. Among them are:
1. elimination of serial encoders and decoders
2. no requirement for a BAUD rate clock
3. inherent synchronization (such as no loss of data due to buffer overflow).
For proper operation, the printer and host must exchange information on a
character-by-character basis. The host initiates the action by presenting to the
printer a character. After a brief setting time, a data strobe is issued by the host
The printer takes the character from its interface circuitry and puts it into the
FIFO buffer. Then a ready signal is sent to the host indicating that another
character may be sent The protocol may be summarized by the following
flowcharts:
3 - 2