EP4CE40 datasheet(225/488 Pages) ALTERA

225 / 488 page

Chapter 8: Configuration and Remote System Upgrades in Cyclone IV Devices

8–61

Configuration

May 2013

Altera Corporation

Cyclone IV Device Handbook,

Volume 1

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.

EP4CE40 Datasheet(PDF) 225 Page - Altera Corporation

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