Telos Zephyr, Руководство пользователя

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Section 11 TECHNICAL INFORMATION 211
and outputs. The digi- pots, CODEC, Xilinx chips, and analog switches are controlled by
some outputs from this chip, while inputs are taken from the LIMIT and PLL circuits for
subsequent processing and display by the CPU.
U4 is the main system program store EPROM, and U8 is the main system RAM, with a
capacity of 32 K bytes. Chip select for these is generated directly by the 801C88. U5 - 7
are EPROMS which are used for storage of software for the DSPs, and the Xilinx chips. As
there is not enough address space available from the CPU for all that is required, we use
two bank select lines, BANKSW0 and BANKSW1 to map the 512 K bytes from the
EPROMs into 128 K byte slots available. These line normally have activity only during
XILINX and/or DSP downloads.
U12 provides further segmentation of the processor’s *PCS1 line for application
to the DSPs. It also generates a periodical DOGSTRB signal for U11, the watchdog chip.
The watchdog resets the CPU in the event that the DOGSTRB signal stops. (The
DOGSTRB is generated by software when it is properly operating. When it “hangs,” the
strobe signal is no longer produced, and the dog goes into action.) U11 provides another
function: It connects the battery to the RAM when system power goes away. This is how
the RAM is able to retain data when the unit is powered- down. The chip select for the
RAM is also routed through this chip, in on pin 13, out on pin 12, for protection – when
power looks to be unreliable, the chip select is gated off, preventing any random
memory- destroying writes.
Don’t remove the processor from its socket without the proper removal tool, as this
may damage the socket and the MPU itself.
(Use PLCC extraction tool from AMP, Cat.
No. 821566- 1, or the lower cost No. 822154- 1. Available from Digi- Key at
1.800.344.4539.)
Motherboard A-F: Power Supply
Two three- terminal regulators, VR1,2, provide clean power to the A/D and D/A chips.
Input voltage is ±12Vdc and output is ±5Vdc.
Motherboard A-F: Parallel I/O
U16 accepts the parallel inputs from the “outside world,” and presents them as proper
logic signals to the UART parallel input pins. This chip can take inputs up to 30 Vdc. The
resistor and diode arrangement on the input allow use with voltages or closures from
the driving equipment.
The ULN- 2003A, U15 is a multiple open- collector darlington driver. It converts the
logic signals from the UART’s parallel outputs to open- collector’s to ground for the
outside world. These have high current drive capability – 500 ma per package.
DSP Cards
The DSP cards use surface- mount technology in order to achieve high density.
Therefore, field servicing of these cards is not supported.