Servo - November 2010

 ;timer on off control
AD_DIP equ 0x6 ;selects if DIP is read
 ;for input select (Bits 1
 ;and 2)
AD_JUS equ 0x7 ;set right if set

We could have easily kept the assembler syntax and tested bits within the UF and CF SRAM locations. In that case, we would use the CCS C compiler’s built-in functions bit_clear, bit_set, and bit_test. For instance, here’s the C code to set UF flag bit ADCR:

bit_set(UF,ADCR);

To test the ADCR bit, we use the built-in function bit_test:

value = bit_test(UF,ADCR);

Clearing and setting the ADCR bit using assember looks like this:

bcf
bsf
UF,ADCR
UF,ADCR

On the other hand, we can make the C source code a bit easier to follow by rounding up all of the flag bits into their respective UF and CF corrals using special C structures:

//User Flags
typedef struct{
 int8  NU:1;
 int8  DBu:1;
 int8  TK:1;
 int8  SW_CH:1;
 int8  BCD0:1;
 int8  BCD1:1;
 int8  TPWM:1;

 int8  ADCR:1;
}UFFLAGS;

//Control Flags
typedef struct{
 int8  na:3;
 int8  FQ:1;
 int8  TRG:1;

int8  CNT_ON:1;

int8  AD_DIP:1;

 int8  AD_JUS:1;
}CFFLAGS;

//debounce control buffer
//tick set from timer 0
//change in reed switch
//BCD Display Counter
//BCD Display Counter H
//Display and read dip
//switch off
//AD New Read
//used for FQ mode select
//trigger bit used to store
//last trigger
//counter on bit counter
//timer on off control
//selects if DIP is read
//for input select (Bits
//1 and 2)
//set right if set

Once the UF and CF structures are defined, we must instantiate an instance of each of the structures before we can use them. Here’s the code:

UFFLAGSUF;
CFFLAGSCF;

Now, using the CCS compiler, we can set, clear, and test user and control flag bits like this:

UF.ADCR = 1;
CF.CNT_ON = 0;

//set ADCR bit
//clear CNT_ON bit
if(CF.AD_DIP == 1)
{
//do something here
}

Here are the last of the assembler equate statements in the eMate.asm file we’ve been porting:

;***** Display Bit Def
SO0 equ 0x0
SO1 equ 0x1
SO2 equ 0x2
SO3 equ 0x5
SO_SEL equ 0x1

;******* COM PORT

SRX
equ

0x6

STX
equ

0x7

;******** Button Locations
But1 equ 0x2

But2 equ
But3 equ
But4 equ

0x3
0x4
0x0

; BCD bit 0  RC0
; BCD bit 1  RC1
; BCD bit 2  RC2
; BCD bit 3  RC5
; RB1 Control for
; DIP or display
; 1 = Display
; Display Select
; 0 RC6
; Display Select
; 1 RC7

; location of
; buttons on port b

I think you have an idea of what the equivalent C source will look like:

// Display Bit Def
#define SO0 0x00
#define SO1 0x01
#define SO2 0x02
#define SO3 0x05
#define SO_SEL 0x01

//COM Port
#define SRX 0x06
#define STX 0x07
//Button Locations
#define But1 0x02

#define But2
#define But3
#define But4

0x03
0x04
0x00

//BCD bit 0 RC0
//BCD bit 1 RC1
//BCD bit 2 RC2
//BCD bit 3 RC5
//RB1 Control for DIP or
//Ddisplay 1 = Display
//Display Select 0 RC6
//display Select 1 RC7

//location of buttons on
//port b

What’s Next?

We’ve ported what I believe to be one of the most important parts of any program — the initial definitions. The next set of assembler code we will tackle is the application setup portion of the eMate.asm file. The eM8 application is made up of a number of peripheral-specific include files which are called from eMate.asm. So, as we move through the eMate.asm code, we’ll branch off and port dependent peripheral-specific include files as we come to them. If there is anything exciting we can do with our ported code and the eM8 hardware along the way, you can count on us getting out of the truck and walking down those trails. SV