User's Manual

Page 59 of 83

A Carrier Corp. Company

PART NUMBER T82002163

REV A

TempTale 4 (Epson TT4)

Command Transmission Paradigm

As a method of ensuring data integrity, the unit will always echo commands back to the host

computer as it receives them. In this way the external device will know that the unit received a

specific command correctly. This method allows the host computer to respond in the fastest way.

If the unit echoes back the wrong command, the host computer merely disables communications,

thereby forcing the unit to timeout while waiting for a go signal.

If the command is to be followed by a series of data bytes, such as when the host computer is

writing to the Scratchpad, that data is sent by the host computer upon receiving the echoed back

command. Otherwise a 0 is sent by the host to act as a go command. The unit will then perform

the requested action and return an action status byte. Any data or information as required by the

requested action will follow this byte.

command

External

Device

TempTale

echo back command

0x00 or parameters

execute

command

command status

any additional response data

Status Byte Definitions

A status byte is always returned from the unit upon completing a command. This is a single byte

value. A '0' value indicates successful completion while a non-'0' indicates an error code. Certain

commands require the unit to be in a specific operating mode. If that condition is not satisfied, the

present mode is sent back as an error code. Status bytes are listed in the table below.

Status name Code Description

CMD_SUCCESSFUL 0x00 Returned upon successful completion of command.

Deleted:

RS232

Deleted: