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CoolRunner-II CPLD Family
6
DS090 (v3.1) September 11, 2008
Product Specification
R
software. The AIM minimizes both propagation delay and
power as it makes attachments to the various FBs.
I/O Block
I/O blocks are primarily transceivers. However, each I/O is
either automatically compliant with standard voltage ranges
or can be programmed to become so. See XAPP382 for
detailed information on CoolRunner-II I/Os.
In addition to voltage levels, each input can selectively
arrive through Schmitt-trigger inputs. This adds a small time
delay, but substantially reduces noise on that input pin.
Approximately 500 mV of hysteresis is added when
Schmitt-trigger inputs are selected. All LVCMOS inputs can
have hysteresis input. Hysteresis also allows easy genera-
tion of external clock circuits. The Schmitt-trigger path is
patibility with I/O standards.
Outputs can be directly driven, 3-stated or open-drain con-
figured. A choice of slow or fast slew rate output signal is
also available.
Table 5 summarizes various supported volt-
age standards associated with specific part capacities. All
inputs and disabled outputs are voltage tolerant up to 3.3V.
The CoolRunner-II family supports SSTL2-1, SSTL3-1 and
HSTL-1 high-speed I/O standards in the 128-macrocell and
larger devices.
Figure 4 details the I/O pin, where it is noted
that the inputs requiring comparison to an external refer-
ence voltage are available. These I/O standards all require
VREF pins for proper operation. The CoolRunner-II CPLD
allows any I/O pin to act as a VREF pin, granting the board
layout engineer extra freedom when laying out the pins.
However, if VREF pin placement is not done properly, addi-
tional VREF pins might be required, resulting in a loss of
potential I/O pins or board re-work. See XAPP399 for
details regarding VREF pins and their placement.
VREF has pin-range requirements that must be observed.
The Xilinx software aids designers in remaining within the
proper pin range.
Table 5 summarizes the single ended I/O standard support
and shows which standards require VREF values and board
termination. VREF detail is given in specific data sheets.
Figure 4: CoolRunner-II CPLD I/O Block Diagram
Enabled
To Macrocell
Direct Input
To AIM
4
CTE
PTB
GTS[0:3]
CGND
Open Drain
From Macrocell
VCCIO
VREF
Disabled
Hysteresis
Available on 128 Macrocell Devices and Larger
Global termination
Pullup/Bus-Hold
DS090_04_121201
Table 5: CoolRunner-II CPLD I/O Standard Summary
IOSTANDARD
Attribute
VCCIO
Input VREF
Board Termination Voltage
(VTT)
Schmitt-trigger Support
LVTTL
3.3
N/A
Optional
LVCMOS33
3.3
N/A
Optional
LVCMOS25
2.5
N/A
Optional
LVCMOS18
1.8
N/A
Optional
LVCMOS15
1.5
N/A
Not optional
HSTL_1
1.5
0.75
Not optional
SSTL2_1
2.5
1.25
Not optional
SSTL3_1
3.3
1.5
Not optional