codes are accepted at TTL or 5V CMOS levels. The data inputs are not latched and must be static
during the handshake sequence. The Data Strobe input times the incoming data transfer. When the
printer is not busy (the busy signal is low) the data must be held static on the data pins and the strobe
signal taken low until the busy signal goes high to acknowledge the data transfer. The data strobe
must then be taken high ready to transmit the next byte. Figure 5.1 shows typical connections to a PC
parallel port.
5.2 Serial Data Mode
The serial data input accepts a TTL or 5V CMOS positive true signal. The busy signal will be low
when the printer is ready to accept data. The Ap25 is not suitable for direct connection to a PC RS232
Com. port. (Please refer to ASL for a converter board, or alternatively Able Systems produce an
Ap25S which is the serial RS232 version of the Ap25 and is suitable for direct connection to a PC.)
Figure 5.2 shows typical connections to a PC serial com. port for the Ap25.
Fig. 5.2 Serial Connection to a PC
5.3 Busy Output Signal
The controller asserts the Busy output when the input buffer is one character away from being full.
The following character will, however, be loaded into the input buffer. This avoids any data being lost
due to the host not responding to the busy signal immediately (such as with a double-buffered UART
in a PC).
5.4 Printing modes and data buffer
Character printing modes include graphics, inverted, double height and double width. Graphics mode
is cancelled at the end of every dot line, whereas the combinations of double height and width remain
in force until cancelled by a new command.
The Ap25 will print data before the ESCape code and then implement the new mode selection. The
data buffer accommodates 48 bytes, which can extend over many physical print lines, depending on
the mechanism in use and the data format; and new data can be entering the buffer as previous data
are being printed.
5.5 Character Printing
The Ap25 prints the characters from left to right. The characters fit into a 6 wide
×
10 high matrix.
The standard letter is 5 wide
×
7 high, this provides for a one dot space between each character, a dot
Ap25 Users’ Guide Page 4 of 8
Printer J3
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
NC
NC
NC
D7
Busy
Invert
GND
GND
VCC
Reset
Mech
D0
D1
D2
D3
D4
D5
D6
Serial TTL Data
PC Serial Com. Port
NC
Baud Rate Select
Baud Rate Select
NC
NC
NC
NC
NC
RS232 Serial
Busy
GND
RS232 - TTL
Converter
Converter
TTL - RS232
NC
NC
25 Way D-Type
7
2
Data Transmit
5