User`s guide

Appendix C – Useful registers

The contents of this chapter should be of little interest when using Simulink to generate the

code. Should one ever need to troubleshoot or decide to write segments of code by hand – the

registers shown below are of great interest. The reader should note that this chapter is not to

be considered a full reference guide – but merely a quick explanation of the F2812’s register

structure, a list of some of the most common ones and their functions.

The timer registers include the following: (same principle for timers 2-4)

• Timer 1 Counter Register (T1CNT) Address 7401h

• Timer 1 Compare Register (T1CMPR) Address 7402h

• Timer 1 Period Register (T1PR) Address 7403h

• Timer 1 Control Register (T1CON) Address 7404h

The first three are pretty straightforward – each containing a 16-bit value. T1CON on the

other hand, is well worth a closer look:

T1CON as seen in the Event Manager Reference Guide

Bit(s) Name Description

15:14 FREE, SOFT Emulation control bits

13 Reserved Reads return zero, writes have no effect.

12−11 TMODE1−TMODE0 Count mode selection

10−8 TPS2−TPS0 Input clock prescaler

7 T2SWT1/T4SWT3

6 TENABLE Timer enable

5−4 TCLKS(1,0) Clock source

3−2 TCLD(1,0) Timer compare register reload condition

1 TECMPR Timer compare enable

0 SELT1PR, SELT3PR Period register select

A lot of options are available to the user by setting the correct flags, the register above for

example, offers the choice of external or internal clocks as well as setting the behaviour of the

internal clock. How to set flags was covered briefly in appendix A.