UM0225 datasheet(29/57 Pages) STMICROELECTRONICS

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UM0225

3 Designing with CAPS

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Because of STR91x pin dependencies, some peripherals may become unavailable for

assignment as pins are assigned. CAPS, dynamically, makes the necessary pin assignments

and reassignments. Peripherals no longer available for assignment, due to GPIO resource

limitations, are highlighted in red.

Note:

As a design aid, during pin assignment, you may always choose the Pin Summary tab to

graphically show the current pin assignments. (See Figure 26.: Pin Summary tab).

The header file 91x_conf.H is automatically created for your project. This default header file is

used by the STR9 HAL library to initialize clock source and peripheral usage. You may,

optionally, continue to step 2 of the dialog to create a C-header file. It is recommended that you

create the separate C-header file to be included in your source code to reference the pins and

their respective functions. (See Figure 24.: C-header file create dialog).

Figure 24. C-header file create dialog

Click the Save button to save the C-header file.

To address incremental design and PCB constraints there are two options for fixing pin

assignment.

•

Lock-pin feature

•

Selective pin function assignment

The lock-pin feature gives the user the option to fix a set of assigned pin(s) for the selected

peripheral by preventing CAPS from de-allocating those pins during subsequent peripheral

selection. The benefit of the lock-pin feature, a toggle feature, is to allow the user to lock the

optimal pin grouping assigned by CAPS.

To lock the pin, preventing CAPS pin reassignment, right-click on the desired peripheral in the

assigned list and click the Lock Pin pop-up button, as shown in Figure 25.

Figure 25. Lock and unlock pin toggle dialog

The peripheral mnemonic is grayed when the pin is locked. This is a toggle operation so use

the same mechanism, right-click and click the Unlock Pin pop-up button, to unlock the pin.

The selective pin function assignment option allows advanced users to have full control in

selectively assigning the pin functions of the selected peripheral. This option prevents the pin

function from being re-routed, fixing the pin for PCB layout.

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