X930A Datasheet, PDF (34/38 Pages) Intel Corporation – UNIVERSAL SERIAL BUS MICROCONTROLLER

8x930Ax UNIVERSAL SERIAL BUS (USB) MICROCONTROLLER
6.0 THERMAL CHARACTERISTICS
This microcontroller operates over the commercial
temperature range from 0^oC to 70^oC. All thermal
impedance data (Table 16) is approximate for static
air conditions at 1 watt of power dissipation. Values
change depending on operating conditions and
application requirements. The Intel Packaging
Handbook (order number 240800) describes Intel’s
thermal impedance test methodology. The
Components Quality and Reliability Handbook
(order number 210997) provides quality and
reliability information.
Table 16. Thermal Characteristics
Package Type
θ_JA
θ_JC
68-pin PLCC
N/A
N/A
7.0 PRODUCT REFERENCE
This section lists design considerations for the
8x930Ax Universal Serial Bus microcontroller.
7.3 Setting FFRC Bit Clears Only the
Oldest Packet in the FIFO
If the receive FIFO is set as a dual packet mode, it
can receive two packets. Setting FFRC to indicate
FIFO Read Complete will not flush the entire FIFO,
only the oldest packet will be flushed. The read
marker will be advanced to the location of the read
pointer.
7.4 Series Resistor Requirement for
Impedance Matching
Per the USB 1.0 specification (page 111, section
7.1.1.1), the impedance of the differential driver
must be between 29 and 44 Ohms. To match the
cable impedance, a series resistor of 27 to 33 Ohms
should be connected to each USB line; i.e., on D_P0
(pin 55) and on D_M0 (pin 54). If the USB line is
improperly terminated or not matched, signal fidelity
will suffer. This can be seen on the scope as
excessive overshoot and undershoot. This will
potentially introduce bit errors.
7.1 External Bus Timing and
Peripheral Timing Affected by
PLLSEL2:0 Selection
PLLSEL2 (pin43), PLLSEL1 (pin 42), and PLLSEL0
(pin 44) determine the 8x930Ax internal CPU
operating frequency. The selected CPU operating
frequency also influences all the peripherals. If the
PLLSEL2:0 pins of the 8x930Ax are set to 110, then
the internal clock frequency is 12MHz, and one
state time equals one clock time (please refer to
Table 8 on page 12). Therefore, all internal and
external instruction times for the timer, serial port,
PCA, are two times faster than with other
PLLSEL2:0 selections. Refer to the 8x930Ax,
8x930Hx Universal Serial Bus Microcontroller
User’s Manual for the new peripheral timing
formulas.
7.2 Low Clock Mode Frequency
In low clock mode, the CPU and peripherals run at 3
MHz. All external bus accesses are affected,
including instruction fetch, data read/write, and
peripheral timing. Please refer to Table 8 on page
12 for the relationship of 3 MHz CPU and peripheral
timing (T_CLK) to state times. One peripheral cycle is
6 state times.
7.5 Pullup Requirement for Full
Speed Device and Low Speed
Device
The pullup is a USB requirement to allow the host to
identify which devices are low speed and which are
full speed in order to communicate at the appro-
priate data rate. For Full Speed devices (12 Mbps)
use a 1.5K pullup resistor (to 3.0 V – 3.6 V) on the
D_P0 line. For Low Speed devices (1.5Mbps), use a
1.5K pullup resistor (to 3.0 V – 3.6 V) on the D_M0
line.
7.6 Powerdown Mode Cannot Be
Invoked Before USB Suspend
If the 8x930Ax is put into powerdown mode prior to
receiving a USB Suspend signal from the host, a
USB Resume will not properly wake up the
8x930Ax from powerdown mode.
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ADVANCE INFORMATION