36 Altera Corporation
Board Components Nios Development Board Reference Manual, Cyclone Edition
A socketed 50 MHz free-running oscillator (Y2) supplies the fundamental
operating frequency, and a clock buffer (U2) drives zero-skew clock
signals to various points on the board.
The Cyclone device can synthesize a new clock signal internally using on-
chip PLLs, and distribute the clock to various locations on the board by
outputting the clock signal to the IO_PLL1_OUT0_p pin. The clock buffer
drives this signal to the following locations:
■ The PROTO1_CLKIN and PROTO2_CLKIN pins on the expansion
prototype connectors, allowing a user-defined clock to drive each of
the expansion prototype headers.
■ The clock input for the SDRAM memory (U57), allowing SDRAM to
run at a different rate than the clock oscillator.
■ The CLK0 clock input on the Cyclone device.
The Cyclone device can also supply a clock from the IO_PLL2_OUT0_p
pin to the SDRAM (U57).
1 The 50 MHz oscillator (Y2) is socketed and can be changed by the
user. However, the MAX EPM7128AE device configuration
control circuit and other Altera reference designs are not
guaranteed to work at different frequencies. It is the user’s
responsibility to accommodate a new clock oscillator when
designing a system.
JTAG
Connections
The Nios development board, has two 10-pin JTAG headers (J5 and J24)
compatible with the Altera ByteBlaster II download cable. Each JTAG
header connects to one Altera device and forms a single-device JTAG
chain. J24 connects to the Cyclone device (U60), and J5 connects to the
MAX EPM7128AE device (U3).
JTAG to Cyclone Device (J24)
J24 connects to the JTAG pins (TCK, TDI, TDO, TMS, TRST) of the Cyclone
device (U60) as shown in Figure 22 on page 37. Altera Quartus II software
can directly configure the Cyclone device with a new hardware image via
an Altera ByteBlaster II download cable as shown in Figure 23 on page 37.
In addition, Nios embedded processor debugger software can access the
Nios OCI debug module via a download cable connected to the J24 JTAG
connector.
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