Altera Cyclone IV Device Handbook page 222

8–58
Use the ACTIVE_DISENGAGE instruction with the CONFIG_IO instruction to interrupt
configuration.
CONFIG_IO usage scenarios.
Table 8–16. JTAG CONFIG_IO (without JTAG_PROGRAM) Instruction Flows
JTAG Instruction
ACTIVE_DISENGAGE
CONFIG_IO
JTAG Boundary Scan
Instructions (no
JTAG_PROGRAM)
ACTIVE_ENGAGE
PULSE_NCONFIG
Pulse nCONFIG pin
JTAG TAP Reset
Notes to Table 8–16:
(1) You must execute "R" indicates that the instruction before the next instruction, "O" indicates the optional instruction, "A" indicates
that the instruction must be executed, and "NA" indicates that the instruction is not allowed in this mode.
(2) Required if you use ACTIVE_DISENGAGE.
(3) Neither of the instruction is required if you use ACTIVE_ENGAGE.
The CONFIG_IO instruction does not hold nSTATUS low until reconfiguration. You must
disengage the AS or AP configuration controller by issuing the ACTIVE_DISENGAGE and
ACTIVE_ENGAGE instructions when active configuration is interrupted. You must issue
the ACTIVE_DISENGAGE instruction alone or prior to the CONFIG_IO instruction if the
JTAG_PROGRAM instruction is to be issued later
configuration controllers into the idle state. The active configuration controller is re-
engaged after user mode is reached through JTAG programming
1
While executing the CONFIG_IO instruction, all user I/Os are tri-stated.
If reconfiguration after interruption is performed using configuration modes (rather
than using JTAG_PROGRAM), it is not necessary to issue the ACTIVE_DISENGAGE
instruction prior to CONFIG_IO. You can start reconfiguration by either pulling nCONFIG
low for at least 500 ns or issuing the PULSE_NCONFIG instruction. If the
ACTIVE_DISENGAGE instruction was issued and the JTAG_PROGRAM instruction fails to
enter user mode, you must issue the ACTIVE_ENGAGE instruction to reactivate the active
configuration controller. Issuing the ACTIVE_ENGAGE instruction also triggers
reconfiguration in configuration modes; therefore, it is not necessary to pull nCONFIG
low or issue the PULSE_NCONFIG instruction.
Cyclone IV Device Handbook,
Volume 1
Chapter 8: Configuration and Remote System Upgrades in Cyclone IV Devices
Table 8–16 lists the sequence of instructions to use for various
Configuration Scheme and Current State of the Cyclone IV Device
Prior to User Mode
(Interrupting Configuration)
PS FPP AS AP
O O O 0
R R R R
O O O 0
(2) (2)
R R
(3) (3)
A A A A
(3) (3)
A A
R R R R
(1)
User Mode
PS FPP AS AP
O O O 0
R R R R
O O O 0
(2) (2)
R R
A A O 0
O 0
R R R R
(Table 8–17). This puts the active
Configuration
Power Up
PS FPP AS AP
— — — —
NA NA NA NA
— — — —
— — — —
— — — —
— — — —
— — — —
(Table 8–17).
May 2013 Altera Corporation