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Cmod™ Board Reference Manual
Revised October 26, 2012
This manual applies to the Cmod rev. D
Overview
Cmod boards combine a Xilinx CPLD, a JTAG programming port, and power supply circuits in a convenient 600-mil,
40-pin DIP package. Cmods are ideally suited for breadboard or other prototype circuit designs where the use of
small surface mount packages is impractical. All Cmod boards include:
Features include:
•
•
•
•
•
The Cmod board.
•
A single 3.3V supply voltage (voltage regulation
provided on Cmod board where required);
Adequate bypass capacitance on all CPLD voltage
supply pins;
All available user I/O signals brought out to DIP pins;
Once programmed, CPLD designs are non-volatile;
Designs can easily be ported between Cmods using
different CPLD device families;
All Cmod boards are compatible with the free Xilinx
WebPack tools.
Cmods were created to make the latest Xilinx CPLDs more practical for experimental and prototype circuits. They
can plug directly in to breadboards or IC sockets, and they can mate with the Digilent Ceres™ board to utilize a
collection of ready-made I/O circuits. Cmods are available with CoolRunner-II CPLD C2. C-Mod boards are
especially useful for investigating designs across a variety of CPLD families.
1
1.8VDC
regulator
(C2 Mod)
Functional Description
Cmod boards, which measure just 0.7” by 2.16”, allow designers to
experiment with CPLD-based designs in a variety of state-of-the art devices.
Designs can easily be ported from one Cmod to another, so that design
performance in different devices can be compared and contrasted. The 40pin DIP form factor allows Cmods to be used in breadboard or other
through-hole circuits where surface-mount devices are impractical. They can
be configured with a wide range logic circuits, from simple logic functions to
sequential controllers. All available CPLD I/O signals are routed to the 40-pin
DIP connections.
JTAG
Connector
CPLD in VQ44 Package
CMod-C2:
XC2C64
40 pin, 600-mil DIP Connector
Figure 2. Cmod circuit board block diagram.
DOC#: 502-047
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Other product and company names mentioned may be trademarks of their respective owners.
Page 1 of 4
Cmod™ Board Reference Manual
When used in conjunction with the Ceres board, Cmods can be used to rapidly implement CPLD based circuits, or
to gain exposure to Xilinx CAD tools and CPLD-oriented design methods. The Ceres board provides Cmods with a
power supply, a clock source, input buttons and switches, and various output LEDs. The Ceres/Cmod combination
makes an excellent platform for use in teaching labs.
Cmods are programmed with a sample design during manufacturing. This design, available at the Digilent website,
can be used to verify Cmod/Ceres function. It also provides a simple reference design example of a Xilinx project.
3
CPLD Configuration
Cmod boards contain a JTAG port for CPLD programming. The port consists of a pattern of six offset holes that are
not loaded with header pins. To use this port, a row of six unattached header pins can be inserted into the end of a
JTAG3 (or other) cable, and the other side of the header can be inserted into the offset hole patterns. Once the
Cmod board is connected to the PC via the JTAG cable, the configuration software will automatically detect the
CPLD.
JTAG
Signal
XC2C64
pin
XC9572XL
pin
XCR3064
pin
TCK
TDI
TDO
TMS
11
9
24
10
11
9
24
10
26
1
32
7
Table 1. CPLD JTAG pins.
To configure the board from a computer using the JTAG port, first ensure the Cmod is powered with a 3.3V supply
(such as provided by the Ceres board), and that the JTAG cable is properly connected to the Cmod and to the
computer. Start the configuration program (e.g., the iMPACT programmer available in the Xilinx WebPack tools),
and the board will be auto-detected. Device programming and other JTAG operations are available in a pull-down
menu made visible by right clicking on the device graphic in the programmer window.
JTAG3
Cable
6-pin
header
C-Mod
Figure 3. JTAG cable used with Cmod.
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Other product and company names mentioned may be trademarks of their respective owners.
Page 2 of 4
Cmod™ Board Reference Manual
4
Power Supplies
Cmod boards require a single 3.3V supply on pin 20, and a single GND on pin 21. Current consumption is
dependent on CPLD family, CPLD configuration, and external circuits. In most cases, current will be far less than
100mA, but the Xilinx data sheets for the particular CPLD should be referenced for more information.
5
CPLDs
Cmod boards are available with CoolRunner-2, CoolRunner (XPLA), and XC95 CPLDs. All available CPLD I/O signals
are routed to the DIP connector, and the JTAG signals are routed to a programming connector. CPLD pinouts are
provided in tables 2 and 3 below. Please see the data sheets for the CPLDs available at the Xilinx website for more
information.
DIP
PIN
Ceres
Signal
C-Mod C2
C-Mod 95
C-Mod XCR
XC2C64
pin
type
Function
Block
XC9572XL
pin
type
Function
Block
XCR3064 pin
type
Function
Block
1
CA
12
IO
4
12
IO
3
12
IO
4
2
CB
13
IO
4
13
IO
3
13
IO
4
3
CC
14
IO
4
14
IO
3
14
IO
4
4
CD
16
IO
4
16
IO
3
15
IO
4
7
IO
3
5
6
7
8
9
CE
18
IO
3
18
IO
3
18
IO
3
10
CF
19
IO
3
19
IO
4
19
IO
3
11
CG
20
IO
3
20
IO
4
20
IO
3
12
AN3
21
IO
3
21
IO
4
21
IO
3
13
AN2
22
IO
3
22
IO
4
22
IO
3
14
AN1
23
IO
3
23
IO
4
23
IO
3
15
AN0
27
IO
3
27
IO
4
25
IO
3
16
SW7
28
IO
3
28
IO
4
27
IO
1
17
DP
29
IO
3
29
IO
2
18
BTN3
30
GSR
1
30
IO
2
6
IO
2
20
15
VCC
26
VCCIO
9,17,29, 41
VCC
20
7,26
VCCIO
15,35
VCCINT
20
35
VAUX
19
21
4,17,25
GND
4,17,25
GND
16,24,36
GND
22
SW6
31
GTS2
1
31
IO
2
28
IO
1
23
SW5
32
GTS3
1
32
IO
2
30
IO
1
24
SW4
33
GTS0
1
33
GSR
1
31
IO
1
25
SW3
34
GTS1
1
34
GTS2
2
33
IO
1
26
SW2
36
IO
1
36
GTS1
2
34
IO
1
27
SW1
37
IO
1
37
IO
2
35
IO
1
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Other product and company names mentioned may be trademarks of their respective owners.
Page 3 of 4
Cmod™ Board Reference Manual
28
BTN2
38
IO
1
38
IO
2
37
IN3/CLK3
29
SW0
39
IO
2
39
IO
1
42
IO
2
30
LED7
40
IO
2
40
IO
1
43
IO
2
31
LED6
41
IO
2
41
IO
1
44
IO
2
32
LED5
42
IO
2
42
IO
1
2
IO
2
33
BTN0
43
GCK0
2
43
GCK1
1
40
IN0/CLK0
34
BTN1
44
GCK1
2
44
GCK2
1
39
IN1/CLK1
35
MCLK
1
GCK2
2
1
GCK3
1
38
IN2/CLK2
36
LED4
2
IO
2
2
IO
1
3
IO
2
37
LED3
3
IO
2
3
IO
1
5
IO
2
38
LED2
5
IO
4
5
IO
3
8
IO
4
39
LED1
6
IO
4
6
IO
3
10
IO
4
40
LED0
8
IO
4
8
IO
3
11
IO
4
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Other product and company names mentioned may be trademarks of their respective owners.
Page 4 of 4