11–4
Altera Corporation
Stratix Device Handbook, Volume 2
July 2005
Device Configuration Overview
related I/O banks (3, 4, 7, and 8) where the following pins reside: TDI,
TMS
, TCK, TRST, MSEL0, MSEL1, MSEL2, nCONFIG, nCE, DCLK, PLL_ENA,
CONF_DONE
, nSTATUS. The VCCSEL pin can be pulled to 1.5, 1.8, 2.5, or
3.3-V for a logic high level. There is an internal 2.5-k
Ωpull-down resistor
on VCCSEL. Therefore, if you are using a pull-up resister to pull up this
signal, you need to use a 1-k
Ω resistor.
VCCSEL
also sets the power-on-reset (POR) trip point for all the
configuration related I/O banks (3, 4, 7, and 8), ensuring that these I/O
banks have powered up to the appropriate voltage levels before
configuration begins. Upon power-up, the FPGA does not release
nSTATUS
until VCCINT and all of the VCCIOs of the configuration I/O
banks are above their POR trip points. If you set VCCSEL to ground (logic
low), this sets the POR trip point for all configuration I/O banks to a
voltage consistent with 3.3-V/2.5-V signaling. When VCCSEL = 0, the
POR trip point for these I/O banks may be as high as 1.8 V. If VCCIO of any
of the configuration banks is set to 1.8 or 1.5 V, the voltage supplied to this
I/O bank(s) may never reach the POR trip point, which will not allow the
FPGA to begin configuration.
1
If the VCCIO of I/O banks 3, 4, 7, or 8 is set to 1.5 or 1.8 V and the
configuration signals used require 3.3-V or 2.5-V signaling you
should set VCCSEL to VCC (logic high) in order to lower the POR
trip point to enable successful configuration.
Table 11–3 shows how you should set the VCCSEL depending on the
VCCIO setting of the configuration I/O banks and your configuration
input signaling voltages.
The VCCSEL signal does not control any of the dual-purpose pins,
including the dual-purpose configuration pins, such as the DATA[7..0]
and PPA pins (nWS, nRS, CS, nCS, and RDYnBSY). During configuration,
these dual-purpose pins drive out voltage levels corresponding to the
VCCIO supply voltage that powers the I/O bank containing the pin. After
configuration, the dual-purpose pins inherit the I/O standards specified
in the design.
Table 11–3. VCCSEL Setting
VCCIO (banks 3,4,7,8)
Configuration Input
Signaling Voltage
VCCSEL
3.3-V/2.5-V
GND
1.8-V/1.5-V
3.3-V/2.5-V/1.8-V/1.5-V
VCC
3.3-V/2.5-V
1.8-V/1.5-V
Not Supported