Intermec CK30 Service Manual page 96

Chapter 4 — Theory of Operation
86
This is specifically not a CK30 requirement, but is expected to be a
requirement for future products, which will all use the same docking
connector.
• Undecoded scanners use the FPGA count gathering logic (See "1D
DBP Scanner Interface" on page 78). When an undecoded scanner is
installed on the docking connector, the TETHERED _PRESENT
signal is asserted. Software senses this and configures the FPGA to
switch its count gathering logic from the internal scanner to the tethered
scanner DBP (video) and SOS signals (TETH_DBP and TETH_SOS)
through Schmitt-trigger U9. This action also drives low the FPGA
control line to analog switch U10, isolating the internal scanner from
the ILLUM_LASEN_RTS and SPEED_RANGE_GDRD signals now
being used to control the tethered scanner. (Actually, U10 would
normally already be "open" if internal scanner power is off.)
• Decoded scanners are supported as serial (true RS-232) devices using
RS-232 buffer chip U23 and the "FF" UART signals on the PXA255
normally used for serial dock communications (See "RS-232 Port" on
page 89). Note that this is not the same as the "ST" UART used for
tethered decoded scanners brought in through the 10-pin Stewart port.
• See "Dock Interface" on page 87 for docking connector pin-out and
tethered scanner power details.
Dock Scanner Auto-Detect
A TETH_PRESENT pin is provided on 26-pin docking connector J13 to
indicate when an undecoded tethered scanner is plugged into the docking
connector:
TETH_PRESENT Description
0 Scanner installed:
•
FPGA count gathering logic takes its DBP and SOS inputs
from TETH_DBP and TETH_SOS (from docking
connector).
•
SPEED_RANGE_GDRD, ILLUM_LASEN_RTS, and
SCAN_TRIG signals are isolated from the internal scanner.
•
Software turns off power to the internal scanner (exception:
IT4000).
1 Scanner removed:
•
FPGA count gathering logic takes its DBP and SOS inputs
from the internal scanner.
•
SPEED_RANGE_GDRD, ILLUM_LASEN_RTS, and
SCAN_TRIG signals are connected through to the internal
scanner.
•
Software turns on power to the internal scanner (when
scanning is started)
CK30 Handheld Computer Service Manual