DF69 datasheet(24/106 Pages) PADAUK

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DF69

DC Fan Controller

5-1-1. Program Counter

Program Counter (PC) is the unit that contains the address of an instruction to be executed next. The

program counter is automatically incremented at each instruction cycle so that instructions are retrieved

sequentially from the program memory. Certain instructions, such as branches and subroutine calls, interrupt

the sequence by placing a new value in the program counter. The bit length of the program counter is 12 for

DF69. The program counter of FPP0 is 0 after hardware reset, 1 for FPP1, 2 for FPP2, 3 for FPP3, 4 for

FPP4, 5 for FPP5, 6 for FPP6 and 7 for FPP7. Whenever interrupt event happens, only FPP0 will be

informed and its program counter will jump to ’h10 for interrupt service routine. All the FPP units have its own

program counter to control the program execution sequence.

5-1-2. Stack Pointer

The stack pointer in each processing unit is used to point the top of the stack area where the local variables

and parameters to subroutines are stored; the stack pointer register (sp) is located in IO address 0x02h. The

bit number of stack pointer is 8 bit and data memory is 208 bytes; therefore, the stack memory should be

defined within 208 bytes from 0x00h address. The stack memory of DF69 for each FPP unit can be assigned

by user via stack pointer register, means that the depth of stack pointer for each FPP unit is adjustable in

order to optimize system performance. The following example shows how to define the stack in the ASM

(assembly language) project:

﹒ROMADR 0

GOTO

FPPA0

GOTO

FPPA1

...

﹒RAMADR 0

// Address must be less than 0x100

WORD

Stack0 [1]

// one WORD

WORD

Stack1 [2]

// two WORD

...

FPPA0:

Stack0;

// assign Stack0 for FPPA0,

// one level call because of Stack0[1]

...

call

function1

...

FPPA1:

Stack1;

// assign Stack1 for FPPA1,

// two level call because of Stack1[2]

...

call

function2

...

Page 24 of 106

PDK-DS-DF69_V003 – Apr. 18, 2018

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