
Altera Corporation
2–95
May 2007
Stratix II Device Handbook, Volume 1
Stratix II Architecture
For JTAG chains, the TDO pin of the first device drives the TDI pin of the
second device in the chain. The VCCSEL input on JTAG input I/O cells
(TCK, TMS, TDI, and TRST) is internally hardwired to GND selecting the
3.3-V/2.5-V input buffer powered by VCCPD. The ideal case is to have the
VCCIO of the TDO bank from the first device to match the VCCSEL settings
for TDI on the second device, but that may not be possible depending on
the application.
Table 2–20 contains board design recommendations to
ensure proper JTAG chain operation.
Table 2–19. Board Design Recommendations for nCEO
nCE Input Buffer Power in I/O
Bank 3
Stratix II nCEO VCCIO Voltage Level in I/O Bank 7
VCCIO =
3.3 V
VCCIO =
2.5 V
VCCIO =
1.8 V
VCCIO =
1.5 V
VCCIO =
1.2 V
VCCSEL
high
(VCCIO Bank 3 = 1.5 V)
vv
VCCSEL
high
(VCCIO Bank 3 = 1.8 V)
vv
Level shifter
required
VCCSEL
low
(nCE Powered by VCCPD = 3.3V)
v
Level shifter
required
Level shifter
required
(1)
Input buffer is 3.3-V tolerant.
(2)
The nCEO output buffer meets VOH (MIN) = 2.4 V.
(3)
Input buffer is 2.5-V tolerant.
(4)
The nCEO output buffer meets VOH (MIN) = 2.0 V.
(5)
Input buffer is 1.8-V tolerant.
(6)
An external 250-
Ω pull-up resistor is not required, but recommended if signal levels on the board are not optimal.
Table 2–20. Supported TDO/TDI Voltage Combinations (Part 1 of 2)
Device
TDI Input
Buffer Power
Stratix II TDO VCCIO Voltage Level in I/O Bank 4
VCCIO = 3.3 V VCCIO = 2.5 V VCCIO = 1.8 V VCCIO = 1.5 V VCCIO = 1.2 V
Stratix II
Always
VCCPD (3.3V)
Level shifter
required
Level shifter
required