EP4CE30F29C7N Datasheet, PDF (225/488 Pages) Altera Corporation – Cyclone IV Device Handbook, Volume 1

Chapter 8: Configuration and Remote System Upgrades in Cyclone IV Devices
Configuration
8–61
EN_ACTIVE_CLK
The EN_ACTIVE_CLK instruction causes the CLKUSR pin signal to replace the internal
oscillator as the clock source. When using the EN_ACTIVE_CLK instruction, you must
enable the internal oscillator for the clock change to occur. After this instruction is
issued, other JTAG instructions can be issued while the 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 POR.
DIS_ACTIVE_CLK
The DIS_ACTIVE_CLK instruction breaks the CLKUSR enable latch set by the
EN_ACTIVE_CLK instruction and causes the clock source to revert back to the internal
oscillator. After the DIS_ACTIVE_CLK instruction is issued, you must continue to clock
the CLKUSR pin for 10 clock cycles.
Changing the Start Boot Address of the AP Flash
In the AP configuration scheme (for Cyclone IV E devices only), you can change the
default configuration boot address of the parallel flash memory to any desired
address using the APFC_BOOT_ADDR JTAG instruction.
APFC_BOOT_ADDR
The APFC_BOOT_ADDR instruction is for Cyclone IV E devices only and allows you to
define 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, the TDI and TDO pins 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 (in the LSB direction) by two bits versus the 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 0s are attached in the end as LSB, thereby
pushing the shifted-in boot address to the left by two bits, which become the actual
AP boot address the AP controller gets.
If you have enabled the remote update feature, the APFC_BOOT_ADDR instruction sets
the boot address for the factory configuration only.
1 The APFC_BOOT_ADDR instruction is retained after reconfiguration while the system
board is still powered on. However, you must reprogram the instruction whenever
you restart the system board.
May 2013 Altera Corporation
Cyclone IV Device Handbook,
Volume 1