10
DS077-2 (v3.0) August 9, 2013
Product Specification
Spartan-IIE FPGA Family: Functional Description
R
— OBSOLETE — OBSOLETE — OBSOLETE — OBSOLETE —
Input/Output Block
The Spartan-IIE FPGA IOB, as seen in
Figure 4, features
inputs and outputs that support a wide variety of I/O signal-
ing standards. These high-speed inputs and outputs are
capable of supporting various state of the art memory and
bus interfaces. The default standard is LVTTL.
Table 3 lists
several of the standards which are supported along with the
required reference (VREF), output (VCCO) and board termi-
nation (VTT) voltages needed to meet the standard. For
more details on the I/O standards and termination applica-
tion examples, see
XAPP179, "Using SelectIO Interfaces in
Spartan-II and Spartan-IIE FPGAs."
The three IOB registers function either as edge-triggered
D-type flip-flops or as level-sensitive latches. Each IOB has
a clock signal (CLK) shared by the three registers and inde-
pendent Clock Enable (CE) signals for each register.
In addition to the CLK and CE control signals, the three reg-
isters share a Set/Reset (SR). For each register, this signal
can be independently configured as a synchronous Set, a
synchronous Reset, an asynchronous Preset, or an asyn-
chronous Clear.
A feature not shown in the block diagram, but controlled by
the software, is polarity control. The input and output buffers
and all of the IOB control signals have independent polarity
controls.
Figure 4: Spartan-IIE Input/Output Block (IOB)
Package Pin
Package
Pin
Package Pin
D
CK
EC
SR
Q
D
CK
EC
SR
Q
D
CK
EC
SR
Q
Programmable
Bias and
ESD Network
VCCO
I/O
I/O, VREF
Internal
Reference
To Next I/O
To Other
External VREF Inputs
of Bank
Notes:
1. For some I/O standards.
Programmable
Input Buffer
Programmable
Output Buffer
Programmable
Delay
VCC
VCC(1)
OE
SR
O
OCE
I
ICE
IQ
CLK
TCE
T
DS077-2_01_051501
TFF
OFF
IFF
Table 3: Standards Supported by I/O (Typical Values)
I/O Standard
Input
Reference
Voltage
(VREF)
Input
Voltage
(VCCO)
Output
Source
Voltage
(VCCO)
Board
Termination
Voltage
(VTT)
LVTTL (2-24 mA)
N/A
3.3
N/A
LVCMOS2
N/A
2.5
N/A
LVCMOS18
N/A
1.8
N/A
PCI (3V,
33 MHz/66 MHz)
N/A
3.3
N/A
GTL
0.8
N/A
1.2
GTL+
1.0
N/A
1.5
HSTL Class I
0.75
N/A
1.5
0.75
HSTL Class III
0.9
N/A
1.5
HSTL Class IV
0.9
N/A
1.5
SSTL3 Class I
and II
1.5
N/A
3.3
1.5
SSTL2 Class I
and II
1.25
N/A
2.5
1.25
CTT
1.5
N/A
3.3
1.5
AGP
1.32
N/A
3.3
N/A
LVDS, Bus LVDS
N/A
2.5
N/A
LVPECL
N/A
3.3
N/A