UQC113S2

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UQC113S2

• Interrupt Programming on 68307

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68307 Interrupt Handling

• The 68307 has 2 distinct parts to the structure
  of its interrupt handling
• The standard 68000 core, called the EC000 core
  processor
• The 68307 Interrupt controller

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Interrupt Handling
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Order of Events

1. The Interrupt Controller collects events from on
   and off chip peripherals, orders them and send
   the highest priority to the EC000 core.
2. The EC000 core responds with and Interrupt
   Acknowledge (IACK) after completing the current
   instruction

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Order of Events

1. The Interrupt Controller recognises the IACK and
   sends the interrupt vetor number of the highest
   priority interrupt
2. The EC000 core gets the vector, and reads the
   address of the ISR in the vector table and
   executes that routine

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An Interrupt from Timer 2
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Generating Interrupts

• Firstly the peripheral must be set up to generate
  interrupts
• The Peripheral Interrupt Control Register (PICR)
  must also be initialised for that particular
  peripheral
• The PICR will have the Interrupt Priority Level
  (IPL) for each interrupting peripheral

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Peripheral Interrupt Control Register

• T1 Timer 1, T2 Timer 2, UA UART, MB MBUS
• IPL of 000 means no interrupts, 001-111 is the
  IPL for the interrupting peripheral

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Minos Interrupt Handling
irqhandler oldTvec // set as interrupting on
reaching reference value (0xffff) // installs isr
using minos call // sets up interrupts on
Peripheral interrrupt control to IPL 3 void
timer(void) unsigned short
Trr2 unsigned short Tcn2 unsigned
short Tmr2 unsigned short Picr Tmr2
(unsigned short ) 0x100130 Trr2 (unsigned
short ) 0x100132 Tcn2 (unsigned short )
0x100136 Picr (unsigned short )
0x100024 oldTvec _getvect(0x4b) / Save
current handler address / _setvect(0x4b,timeout)
Trr2 (unsigned short) 0xffff Tcn2
(unsigned short) 0x0000 Tmr2 (unsigned
short) 0x801b// 1000000000011011 reset, ints,
restart master clock Picr Picr (unsigned
short) 0x0300// set the ints for timer 2  
 
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Minos Interrupt Handling
int TFLAG OFF   // isr for timer // clear
timer event reg // wiggle led // set global time
flag to 1 void _interrupt timeout(void) unsigne
d char Ter2 // clear the timer event reg bit
for ref value Ter2 (unsigned char )
0x100139 Ter2 (unsigned char) 0x02   //
wiggle led to let us know what is going
on! asm move.w 100018,D1 bchg
8,D1 move.w D1,100018 endasm   // set
global time flag to 1 tick happened TFLAG1

 
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Minos Interrupt Handling
 
void IRQstop( void ) unsigned short
Tmr2   Tmr2 (unsigned short )
0x100130 Tmr2 (unsigned short)
0 _setvect(0x4b,oldTvec)
     
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Creating a Vector

• Once a peripheral has interrupted a vector must
  be generated for it
• This is done by the Programmable Interrupt Vector
  Register (PIVR)
• The 8 bit vector is broken into 2 nibbles
• A high nibble supplied by the system
• A low nibble generated by the peripheral

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Programmable Interrupt Vector Register

• IV7-IV4 are set by the system, 0x40 on the CMS
  boards
• Bits 3-0 are supplied, from a table, for each
  peripheral

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Interrupt Vector Response
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Interrupt Vector Response
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Assembler ISR
include ltstdio.hgt include ltminos.hgt define MBA
SE 0x100000 define PICR (MBASE
0x24) //peripheral interrupt control
register define PIVR (MBASE
0x27) define TMR2 (MBASE 0x130) //timer 2
mode register define TRR2 (MBASE
0x132) //timer 2 reference register define TCN2
(MBASE 0x136) //timer 2 count
register define TER2 (MBASE 0x139) //timer
2 event register define RESET_INT 0x2 //reset
timer interrupts bit define RESET_T 0x0 //reset
(stop) timer   void IRQstop( void ) void
isr(void) void oframe(void) void T2setup( void
) extern int FPOINT unsigned int oldvec
 
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Assembler ISR
main() unsigned int vect_tab1, vect_tab2,
vect_tab3   vect_tab1 (unsigned int)(0x4b
4) // 0x40 PIVR value 0xb timer2 vect_tab2
(unsigned int)(vect_tab1) //get isr from
vector table 1 vect_tab2 (char ) vect_tab2
2 // get rid of the extraneous 2
bytes!! vect_tab3 (unsigned int)(vect_tab2)
// get real ram isr address oldvec
vect_tab3 //Save current handler address
vect_tab3 (unsigned int)isr // install
new isr routine T2setup() while(!ready(fileno
(stdin))) / Loop until key pressed /
T2stop() vect_tab3 oldvec //restore old
hanlder printf("oldvector address x x, x
x, x \n",vect_tab1, vect_tab1,vect_tab2,
vect_tab2, oldvec)
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Assembler ISR
void T2setup( void ) unsigned short
Trr2 unsigned short Tcn2 unsigned
short Tmr2 unsigned short Picr Tmr2
(unsigned short ) TMR2 Trr2 (unsigned short
) TRR2 Tcn2 (unsigned short ) TCN2 Picr
(unsigned short ) PICR Trr2 (unsigned
short) 0xffff //big number to count from
Tcn2 (unsigned short) 0x0000 // reset
counter Tmr2 (unsigned short) 0x801b //
ints, div by 16, prescale 0x80, start Picr
Picr (unsigned short) 0x0100 / /IPL level 1

 
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Assembler ISR
//rather pointless routine called from isr
prints out frame pointer value void
oframe(void) printf("Frame pointer
x\n",FPOINT) fflush(stdout)
   
void T2stop( void ) unsigned short
Tmr2   Tmr2 (unsigned short )TMR2 Tmr2
(unsigned short) RESET_T
 
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Assembler ISR
 
SECTION __UDATA,D XDEF _FPOINT _FPOINT ds.l 1 fr
ame pointer SECTION __CODE,C XREF _oframe
XDEF _isr _isr movem.l a0/d0,-(sp) save
register a0 d0 on the stack move.w 100018,D0 w
iggle led - what else! bchg 8,D0
move.w D0,100018 movea.l 100139,a0 addr
of timer event reg move.b 2,(a0) clear
event move.l a6,_FPOINT save frame pointer
value into global jsr _oframe go and do C
routine movem.l (sp),a0/d0 restore the
regs rte lets get out of here!