Rs-232/422 Interfaces; Esd And Emi Compatibility; Isolation; Operation - GE T2100 Service Manual

RS-232/422 Interfaces

The LTC1334 serves as the Host to IFC board transceiver. It translates the RS422/232
serial protocol voltage levels to TTL levels. The MAX489 is the transceiver for the
processor board to drive communication. It translates RS422 signals to proper TTL
levels.

ESD and EMI Compatibility

The connectors on this board have current limiting resistors and filtering capacitors on
almost every signal to prevent EMI from escaping this board. These components also
limit rise-time and voltages which may come from ESD or other noise sources.

Isolation

The drive serial communication circuit, drive, and elevation control signals share a
common ground that may be attached to the chassis. The Host serial communication,
ESTOP connection, calibration button, and control circuitry are all placed on isolated
power. This ground allocation separates the micro controller ground from the chassis
ground by using opto-couplers allowing at least 4KVAC without breakdown and
double isolation for 250 VAC.

Operation

The processor board's main task is to monitor the proper T2100 Treadmill operation by
testing selected variables from the system. In case of any variable operating out of
specs, the firmware will first detect the event, then log it, and finally stop any further
operation. For speed control, the processor board will act as a translator between the
host and the drive system. For elevation control, the board will act as a controller
by providing proper calibration and by handling elevation increment/decrement
commands received via the host serial port.
Start-Up Sequence
Immediately after power-up, the processor board will start a self-test procedure
where the following subsystems are tested: internal RAM, board temperature, external
serial flash memory, host communication, drive communication, control signals,
elevation, power supply, ESTOP, and calibration. If any of the above tests result in an
abnormal condition, the processor board will stop any further operation and will log
the condition on its external flash memory. After all subsystems are determined to
be operating properly, the processor board will enter in a standby state until a serial
command is received from the host. The processor board will wait until the host
sends a belt start command "B<CR>" to start operations. After receiving the belt start
command, the board will enable the drive by activating the D_DRIVE_EN signal on J2.
After this action, the drive will be activated and in standby state. At this moment
elevation and speed control commands can be sent to the processor board.
Elevation Control
The elevation control process works as follows: The host will send an elevation
command "GXXX0<CR>" to the processor board, the micro controller will interpret this
data in order to enable the elevation subsystem by asserting EN_ELEV signal on J9 and,
based on the actual elevation status, assert/de-assert the UP/DOWN* signal on J9
until the requested elevation is achieved. The elevation range is from 0 to 25% grade.
2021403-120F
T2100 Treadmill
Theory of Operation
65