AM7968 AMD [Advanced Micro Devices], AM7968 Datasheet - Page 103

• Manufacturer Part Number: AM7968
• Description: TAXIchip Integrated Circuits(Transparent Asynchronous Xmitter-Receiver Interface)
• Manufacturer: AMD [Advanced Micro Devices]

TAXI Technical Information Publication #89-05
Subject: TAXIchip Set Crystal Specification
Question:
What are the design considerations for crystals used with TAXIchip set?
Answer:
The TAXIchip’s parallel mode oscillator uses a 4.0 MHz – 17.5 MHz crystal with a
frequency tolerance of 0.1%.
Any crystal will oscillate in either series or parallel mode depending upon the type of
oscillator used. By specifying parallel mode and the load, the manufacturer will calibrate
the crystal in parallel mode at the desired frequency. This could be important in
applications where frequency tolerance is critical due to the fact that the resonant
frequency in parallel mode is typically 0.02% above the series mode frequency.
As discussed in section 3.3, the time required to synchronize the data recovery circuit in
the Receiver is proportional to the delta between the Transmitter frequency and the
Receiver PLL resting frequency. The Receiver resting frequency is typically less than
The crystal specification of 0.1% is meant to be small enough to cause a negligible
effect on lock time while not increasing the crystal cost (0.025% crystals are quite
common). Sometimes tighter frequency and tolerance specifications may be necessary
to meet the user’s system requirements (i.e. FIFO depth, etc.).
More information on crystal specifications for the TAXIchip set may be found in
Section 4.1.1.
A partial list of vendors follows:
Distributor
I.E.A.
Calmax Corp.
Monitor Products
Anderson Electronics
Target Electronics
1% away from its own crystal frequency, due to mismatch between internal circuits.
TAXIchip Integrated Circuits Technical Manual
Typical 12.5 MHz
Part Number
HC18U 12.500
UM-12.5
MM 49XlE12A-12.5
011-668-03260
CC025A-12.5
Phone Number
[phone]
[phone]
[phone]
[phone]
[phone]
AMD
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