Chapter 9 Specifications
DTR protocol
DTR signal “Ready (High)” level requirements:
The following must be satisfied:
• Printer is on line.
• Receive buffer has more than 128 bytes available.
Note: When receive buffer has less than 128 bytes available, DTR signal becomes “Busy
(Low)” level and this “Busy (Low) level is kept until receive buffer has at least 1K bytes
available.
DTR signal “Busy (Low)” level requirements:
The following must be satisfied:
• Printer is in error.
• Printer is in paused state.
• Receive buffer has less than 128 bytes available.
Pin assignment
Pin No. Signal Input/Output Description
1 FG Output Frame ground
7 SGND Output Signal ground
2 TXD Output Signal to transmit data
3 RXD Input Signal to receive data
4 RTS Output Transmission request signal. Pull up to +12V with
3.3Kohm
6 DSR Input Signal active when host computer ready to interface with
printer
20 DTR Output Signal active when printer ready to interface with host
computer
25 VCC Output (Factory use)
