Author: robhamerling
Date: Sun Mar 15 02:47:59 2009
New Revision: 846
Modified:
trunk/doc/html/devicefiles.html
Log:
Several text improvements, especially naming comvention.
Modified: trunk/doc/html/devicefiles.html
==============================================================================
--- trunk/doc/html/devicefiles.html (original)
+++ trunk/doc/html/devicefiles.html Sun Mar 15 02:47:59 2009
@@ -227,10 +227,9 @@
Also some popular aliases for registers are defined, for example: TMR0IF
and
T0IF, TMR0IE and T0IE, etc.
+<h3>PORTx and TRISx</h3>
<p>For all ports and port pins a device independent alias is defined and a
similar direction definition, as the following examples show:
-
-<h3>PORTA and TRISA</h3>
<pre>
var volatile byte PORTA at <addr>
var byte PORTA_low -- low order nibble
@@ -243,6 +242,9 @@
<p>etc. (for all other existing pins and ports)
<h3>GPIO and TRISIO (with the smaller chips)</h3>
+<p>Although the smaller PICs have no 'official' PORTA and TRISA registers,
+the device files contain aliases for these.
+So even with the smaller PICs you can use the names PORTA, pin_A0, etc.
<pre>
var volatile byte GPIO at <addr>
var volatile byte PORTA at GPIO
@@ -256,37 +258,46 @@
</pre>
<p>etc. (for all other existing pins)
-<p>Also some procedures and functions are defined to read and set the lower
-and upper nibbles of ports and their direction:
+<h3>Non-memory-mapped registers</h3>
+<p>Some PICs, especially in the baseline series, are missing some memory
+mapped registers.
+For example the 12-bit core (10Fs, 12F5x, etc) have no memory mapped
+TRISx registers, in stead these PICs have TRISx instructions to set
+the direction of ports or pins.
+This would make it impossible for application programs or function
+libraries to use statements like:
+<pre>
+ PORTA_direction = all_output
+</pre>
+<p>For this reason the device files contain pseudo variables which mimic
+the existence of memory mapped registers.
+This makes it possible to use statement like the one above.
+<p>For example: even though a 16F59 has no addressable TRISC register,
+you can still use
+<pre>
+ pin_C5_direction = output
+</pre>
+<p>
+
+<h3>Nibbles</h3>
+<p>Since frequently the upper and lower 4 bits ('nibble') of a port are
+used as a unit, some procedures and functions are defined to use port
+nibbles as a regular variable and set pin directions by 4:
<pre>
PORTx_low - bits 0..3
PORTx_high - bits 4..7
PORTx_low_direction
PORTx_high_direction
</pre>
+<p>This makes it possible to use statements like:
+<pre>
+ PORTA_low_direction = all_output
+ PORTA_low = "7" -- upper nibble remains unchanged
+</pre>
+<p>Several Jallib function libraries use this facility.
-<p>Notes:
-<ol>
-<li>When you have used Jal before with other device files or libraries
- you may notice some differences in naming convention:
- <ul>
- <li>PORTA is used consistently, while previously PORT_A was a
- popular naming convention especially for PORT_A_low/high,
- PORT_A_direction, etc.
- For individual pins the convention 'pin_Ax' is maintained.
- <li>Subfields of registers have the registername as prefix, like
- <br>var volatile bit INTCON_GIE at INTCON : 7
- </ul>
-<li>See the extra alias declarations for the GPIO and TRISIO registers
- and their bits.
- Programs and function libraries can access the GPIO bits with PORTA
- and pin_Ay names, making it possible to use libraries across a large
- collection of PICmicros.
-</ol>
-
-<h3>MSSP modules</h3>
+<h3>Names of MSSP modules</h3>
<p>Names of registers of MSSP modules have been normalized as follows:
-<p>
<ul>
<li>MSSP module of midrange PICs
<pre>
@@ -315,19 +326,19 @@
</pre>
</ul>
-<h2>Special Features</h2>
-
-<p>The device files contain a number of special procedures for the
-convenience of the JAL programmer.
-Most procedures are in the form of a pseudo variable, some are 'normal'
-procedures.
-Pseudo variables a available for TRISA, TRISB and TRISC and corresponding
-pins for the baseline series of PICmicros.
-This means for example that
-<pre>
- pin_A2_direction = output
-</pre>
-can be used even though these PICs have no TRISA register.
+<h3>Miscellaneous remarks about names</h3>
+<p>When you have used Jal before with other device files or libraries
+you may notice some differences in the naming convention:
+<ul>
+<li>PORTA is used consistently, while previously PORT_A was a
+ popular naming convention especially for PORT_A_low/high,
+ PORT_A_direction, etc.
+ For individual pins the convention 'pin_Ax' is used.
+<li>Subfields of registers have the registername as prefix, like
+ <br>var volatile bit INTCON_GIE at INTCON : 7
+<li>When you hit compile errors related to undefined names, scan the
+ device files to search for 'our' name of the register or port.
+</ul>
<h2>About Port Shadowing</h2>
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