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Communications Reference
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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 Intermec Data Communications Reference Manual (Intermec 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.