Microsemi IGLOO2 - Page 93

Board Design and Layout Checklist
AC393 Application Note Revision 14.0 85
Clocks
30. Crystal Oscillators (External)
– Main crystal oscillator
– Auxiliary (RTC) crystal oscillator (not available in the M2S050T)
RC Oscillators (Internal)
– 1-MHz RC oscillator
– 50-MHz RC oscillator
IGLOO2 devices have only main crystal oscillator without auxiliary (RTC)
crystal oscillator.
For more information about crystal oscillators, see Table 14, page 20.
FPGA Fabric Clock Sources
The input clock frequency range for fabric clock conditioning circuits (FABCCC)
depends on the usage of PLL for output clock generation:
– If the PLL is used, the PLL reference clock frequency must be between 1 MHz
and 200 MHz.
– If the PLL is bypassed, the FABCCC input clock frequency can be up to 400
MHz.
All CCC pins support external oscillators (differential or single ended).
31. Global buffer (GB) can be driven through dedicated global I/Os, CCC, or fabric
(regular I/Os) routing.
The global network is composed of GBs to distribute low-skew clock signals or
high-fanout nets.
Dedicated global I/Os drive the GBs directly and are the primary source for
connecting external clock inputs (to minimize the delay) to the internal global
clock network.
For more information, see UG0449: SmartFusion2 and IGLOO2 Clocking
Resources User Guide.
Reset
32. DEVRST_N – Input
The DEVRST_N pin must have a 10 KΩ pull-up resistor. The pin must not be
left floating. If a push-button switch is used to generate reset, check for switch
de-bounce. For more information about DEVRST_N, see Power Supply Flow,
page 12.
JTAG
33. In the JTAG interface, the VDDI bank supply must be powered up for
programming. The following is a list of pins available for different activities:
– JTAGSEL: Low (pull-down) > ARM Cortex-M3 JTAG; High (pull-up) > FPGA
fabric JTAG.
– TMS: Internal weak pull-up resistor.
– TCK: External pin. Should be pulled-down through 1 KΩ resistor. There is no
internal pull-up resistor for this pin.
– TDI: internal weak pull-up resistor.
– TDO: no internal pull-up resistor.
– TRSTB: internal weak pull-up resistor.
An FP4 or FP5 header (10 pin – 2.54 mm pitch) can be used to connect to
FlashPro4 or FlashPro5.
For more information about JTAG, see Figure 11, page 24 and Table 15,
page 23.
Table 23 • Design Checklist (continued)
S.No. Checklist Yes/No