
7–40
Altera Corporation
Stratix II Device Handbook, Volume 2
January 2008
Active Serial Configuration (Serial Configuration Devices)
Figure 7–13. Multi-Device AS Configuration
(1)
Connect the pull-up resistors to a 3.3-V supply.
(2)
If using an EPCS4 device, MSEL[3..0] should be set to 1101. Refer to
Table 7–11 for more details.
As shown in
Figure 7–13, the nSTATUS and CONF_DONE pins on all target
devices are connected together with external pull-up resistors. These pins
are open-drain bidirectional pins on the devices. When the first device
asserts nCEO (after receiving all of its configuration data), it releases its
CONF_DONE
pin. But the subsequent devices in the chain keep this shared
CONF_DONE
line low until they have received their configuration data.
When all target devices in the chain have received their configuration
data and have released CONF_DONE, the pull-up resistor drives a high
level on this line and all devices simultaneously enter initialization mode.
If an error occurs at any point during configuration, the nSTATUS line is
driven low by the failing device. If you enable the Auto-restart
configuration after error option, reconfiguration of the entire chain begins
after a reset time-out period (a maximum of 100 s). If the Auto-restart
configuration after error
option is turned off, the external system must
monitor nSTATUS for errors and then pulse nCONFIG low to restart
configuration. The external system can pulse nCONFIG if it is under
system control rather than tied to VCC.
1
While you can cascade Stratix II or Stratix II GX devices, serial
configuration devices cannot be cascaded or chained together.
DATA
DCLK
nCS
ASDI
DATA0
DCLK
nCSO
ASDO
Serial Configuration
Device
Stratix II or Stratix II GX
FPGA Master
Stratix II or Stratix II GX
FPGA Slave
10 k
Ω
10 k
Ω
VCC
GND
nCEO
nCE
nSTATUS
CONF_DONE
DATA0
DCLK
nCEO
nCE
nSTATUS
CONF_DONE
10 k
Ω
VCC
nCONFIG
N.C.
(1)
MSEL1
MSEL0
GND
MSEL3
MSEL2
VCC
(2)
MSEL1
MSEL0
GND
MSEL3
MSEL2
VCC