set_io portname [-pinname value][-fixed value][-iostd value][-out_drive value][-slew value][-res_pull value][-out_load value][-skew value][-register value]
portname
Specifies the portname of the I/O macro to set.
-pinname value
Assigns the I/O macro to the specified pin.
-fixed value
Locks or unlocks the location of this I/O. Locked pins are not moved during layout. Therefore, locking this I/O ensures that the specified pin location is used during place-and-route. If this I/O is not currently assigned, then this argument has no effect. The following table shows the acceptable values for the -fixed attribute:
|
Value |
Description |
|
yes |
The location of this I/O is locked |
|
no |
The location of this I/O is unlocked |
-iostd value
Sets the I/O standard for this macro. Choosing a standard allows the software to set other attributes such as the slew rate and output loading. If the voltage standard used with the I/O is not compatible with other I/Os in the I/O bank, then assigning an I/O standard to a port will invalidate its location and automatically unassign the I/O. The following table shows the acceptable values for the -iostd attribute for ProASIC3 devices:
|
Value |
Description |
|
LVTTL |
(Low-Voltage TTL) A general purpose standard (EIA/JESDSA) for 3.3V applications. It uses an LVTTL input buffer and a push-pull output buffer. |
|
LVCMOS33 |
(Low-Voltage CMOS for 3.3 Volts) An extension of the LVCMOS standard (JESD 8-5) used for general-purpose 3.3V applications. |
|
LVCMOS25_50 |
(Low-Voltage CMOS for 2.5 and 5.0 Volts) An extension of the LVCMOS standard (JESD 8-5) used for general-purpose 2.5V and 5.0V applications. |
|
LVCMOS18 |
(Low-Voltage CMOS for 1.8 Volts) An extension of the LVCMOS standard (JESD 8-5) used for general-purpose 1.8V applications. It uses a 3.3V-tolerant CMOS input buffer and a push-pull output buffer. |
|
LVCMOS15 |
(Low-Voltage CMOS for 1.5 volts) An extension of the LVCMOS standard (JESD 8-5) used for general-purpose 1.5V applications. It uses a 3.3V-tolerant CMOS input buffer and a push-pull output buffer. |
|
LVDS |
A moderate-speed differential signalling system, in which the transmitter generates two different voltages which are compared at the receiver. It requires that one data bit be carried through two signal lines; therefore, you need two pins per input or output. It also requires an external resistor termination. The voltage swing between these two signal lines is approximately 350mV (millivolts). |
|
LVPECL |
PECL is another differential I/O standard. It requires that one data bit is carried through two signal lines; therefore, two pins are needed per input or output. It also requires an external resistor termination. The voltage swing between these two signal lines is approximately 850mV. When the power supply is +3.3V, it is commonly referred to as low-voltage PECL (LVPECL). |
|
PCI |
(Peripheral Component Interface) Specifies support for both 33 MHz and 66 MHz PCI bus applications. It uses an LVTTL input buffer and a push-pull output buffer. With the aid of an external resistor, this I/O standard can be 5V-compliant for most families, excluding ProASIC3/E families. |
|
PCIX |
(Peripheral Component Interface Extended) An enhanced version of the PCI specification that can support higher average bandwidth; it increases the speed that data can move within a computer from 66 MHz to 133 MHz. PCIX is backward-compatible, which means that devices can operate at conventional PCI frequencies (33 MHz and 66 MHz). PCIX is also more fault tolerant than PCI. |
-out_drive value
Sets the strength of the output buffer to 2, 4, 6, 8, 12, or 16 in mA, weakest to strongest. The list of I/O standards for which you can change the output drive and the list of values you can assign for each I/O standard is family-specific. Not all I/O standards have a selectable output drive strength. Also, each I/O standard has a different range of legal output drive strength values. The values you can choose from depend on which I/O standard you have specified for this command. See the "Slew and Out_drive Settings" table under "Exceptions" in this topic for possible values. Also, refer to the ProASIC3 datasheet for more information. The following table shows the acceptable values for the -out_drive attribute:
|
Value |
Description |
|
2 |
Sets the output drive strength to 2mA |
|
4 |
Sets the output drive strength to 4mA |
|
6 |
Sets the output drive strength to 6mA |
|
8 |
Sets the output drive strength to 8mA |
|
12 |
Sets the output drive strength to 12mA |
|
16 |
Sets the output drive strength to 16mA |
-slew value
Sets the output slew rate. Slew control affects only the falling edges. Rising edges are not affected. Not all I/O standards have a selectable slew. Whether you can use the slew attribute depends on which I/O standard you have specified for this command. For ProASIC3 devices, this attribute is only available for LVTTL, LVCMOS33, LVCMOS25_50, LVCMOS18, and LVCMOS15 outputs. For any of these I/O standards, the slew can be either high or low. The default is high. See the "Slew and Out_drive Settings" table under "Exceptions" in this topic. Also, refer to the ProASIC3 datasheet for more information. The following table shows the acceptable values for the -slew attribute:
|
Value |
Description |
|
high |
Sets the I/O slew to high |
|
low |
Sets the I/O slew to low |
-res_pull value
Allows you to include a weak resistor for either pull-up or pull-down of the input buffer. Not all I/O standards have a selectable resistor pull option. The following table shows the acceptable values for the -res_pull attribute:
|
Value |
Description |
|
up |
Includes a weak resistor for pull-up of the input buffer |
|
down |
Includes a weak resistor for pull-down of the input buffer |
|
none |
Does not include a weak resistor |
-out_load value
Determines what Timer will use as the loading on the output pin. This attribute applies only to outputs. You can enter a capacitive load as an integral number of picofarads (pF). Specify an integer between 0 and 1023pF. The default is 35pF.
-skew value
Specifies whether there is a fixed additional delay between the enable/disable time for a tristatable I/O. (A tristatable I/O is an I/O with three output states: high, low, and high impedance.) The following table shows the acceptable values for the -skew attribute:
|
Value |
Description |
|
on |
Yes, there is a fixed additional delay |
|
off |
No, there is not a fixed additional delay |
-register value
Specifies whether the register will be combined into the I/O. If this option is yes, the combiner combines the register into the I/O module if possible. This option overrides the default setting in the Compile options. I/O registers are off by default. The following table shows the acceptable values for the -register attribute:
|
Value |
Description |
|
yes |
Register combining is allowed on this I/O |
|
no |
Register combining is not allowed on this I/O |
If an argument is not specified, the value is not changed, as long as it is consistent with other settings. If setting an attribute invalidates the I/Os location, then the I/O is unplaced.
You can specify an out_drive strength and slew rate only for certain I/O standards per family. Not all I/O standards have a selectable output drive strength or slew. The following table shows I/O standards for which you can specify a slew and out_drive setting:
|
I/O Standard |
Out_drive |
Slew |
||||||
|
2 |
4 |
6 |
8 |
12 |
16 |
|||
|
LVTTL |
X |
X |
X |
X |
X |
X |
High |
Low |
|
LVCMOS33 |
X |
X |
X |
X |
X |
X |
High |
Low |
|
LVCMOS25_50 |
X |
X |
X |
X |
X |
- |
High |
Low |
|
LVCMOS18 |
X |
X |
X |
X |
- |
- |
High |
Low |
|
LVCMOS15 |
X |
X |
- |
- |
- |
- |
High |
Low |
set_io IO_in\[2\] -iostd LVPECL -register no -pinname 366 -fixed no