ep3c120f780c8nes Altera Corporation, ep3c120f780c8nes Datasheet - Page 322

• Manufacturer Part Number: ep3c120f780c8nes
• Description: Cyclone Iii Device Family
• Manufacturer: Altera Corporation

Configuring Cyclone III Devices
10–86
Cyclone III Device Handbook, Volume 1
EN_ACTIVE_CLK
The EN_ACTIVE_CLK instruction causes the CLKUSR pin signal to replace
the internal oscillator as the source of clock. After this instruction is
issued, other JTAG instructions can be issued while CLKUSR pin signal
remains as the clock source. The clock source is only reverted back to the
internal oscillator by issuing the DIS_ACTIVE_CLK instruction or a
power-on reset (POR).
DIS_ACTIVE_CLK
The DIS_ACTIVE_CLK instruction breaks the CLKUSR enable latch set by
EN_ACTIVE_CLK instruction and cause the clock source to revert back to
the internal oscillator.
Changing the Start Boot Address of AP Flash
In AP configuration scheme, you can change the default configuration
boot address of the parallel flash memory to any desired address using
the JTAG instruction APFC_BOOT_ADDR.
APFC_BOOT_ADDR
The APFC_BOOT_ADDR instruction defines a start boot address for the
parallel flash memory in the AP configuration scheme.
This instruction shifts in a start boot address for the AP flash. When this
instruction becomes the active instruction, TDI and TDO are connected
through a 22-bit active boot address shift register. The shifted in boot
address bits get loaded into the 22-bit AP boot address update register,
which feeds into the AP controller. The content of the AP boot address
update register can be captured, and shifted out of the active boot address
shift register from TDO.
The boot address in the boot address shift register and update register are
shifted to the right (towards LSB direction) by two bits versus intended
boot address. The reason for this is that the two LSB of the address are not
accessible. When this boot address is fed into the AP controller, two 0's are
attached in the end as least significant bits therefore pushing the shifted-
in boot address to the left by two bits, which becomes the actual AP boot
address the AP controller gets.
When the remote update feature is enabled, the APFC_BOOT_ADDR
instruction sets the boot address for the factory configuration only.
Altera Corporation-Preliminary
March 2007