Communications Protocols; Intermec Standard Protocol - Intermec EasyCoder 4420 User Manual

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Communications Reference
This chapter provides communications reference information you can use to
understand protocols, interfaces, and the serial port.

Communications Protocols

Communications protocols are important because they determine the transmission
standards for communications between the printer and the host. The printer and the host
must use the same protocol and parameters to communicate properly. The printer
supports the flow control and block transfer protocols described in the next sections.
All of these protocols are point-to-point except Multi-Drop. Application programs
and/or ROM BIOS determine which protocols your computer can support. For more
detailed information, refer to the Data Communications Reference Manual (Part No.
044737).

Intermec Standard Protocol

Intermec Standard protocol is a proprietary block transfer/status response protocol. For
each block sent, the host must wait for the appropriate response before sending the next
block (<DC1>). Except for single character status commands (<ENQ> and <VT>),
Standard protocol transmits characters in message blocks beginning with the start of
text (<STX>) character and ending with the end of text (<ETX>) character. Message
blocks can be up to 255 characters, including the start of text and end of text characters.
The printer auto-discriminates between Standard, Polling Mode D, and Multi-Drop
protocols.
The printer returns its highest priority status when it receives a valid block (<STX>
data <ETX>) or when it receives the status request command <ENQ>. When the printer
receives the status dump command (<VT>), the printer returns all active status. The
printer status response time ranges from 30 to 100 ms depending on the complexity of
the received message block. In the case of a transmission error, the printer responds
with a <NAK> and discards the entire message block.
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