HT37B90 datasheet(11/80 Pages) HOLTEK

11 / 80 page

HT37B90/HT37B70/HT37B50/HT37B30

Rev.1.00

June22,2017

If the stack is full and an enabled interrupt takes place,

the interrupt request flag will be recorded but the ac-

knowledge signal will be inhibited. When the Stack

Pointer is decremented, by RET or RETI, the interrupt

will be serviced. This feature prevents stack overflow al-

lowing the programmer to use the structure more easily.

However, when the stack is full, a CALL subroutine in-

struction can still be executed which will result in a stack

overflow. Precautions should be taken to avoid such

cases which might cause unpredictable program

branching.

ArithmeticandLogicUnit - ALU

The arithmetic-logic unit or ALU is a critical area of the

microcontroller that carries out arithmetic and logic op-

erations of the instruction set. Connected to the main

microcontroller data bus, the ALU receives related in-

struction codes and performs the required arithmetic or

logical operations after which the result will be placed in

the specified register. As these ALU calculation or oper-

ations may result in carry, borrow or other status

changes, the status register will be correspondingly up-

dated to reflect these changes. The ALU supports the

followingfunctions:

· Arithmetic operations: ADD, ADDM, ADC, ADCM,

SUB, SUBM, SBC, SBCM, DAA

· Logic operations: AND, OR, XOR, ANDM, ORM,

XORM, CPL, CPLA

· Rotation RRA, RR, RRCA, RRC, RLA, RL, RLCA,

RLC

· IncrementandDecrementINCA,INC, DECA,DEC

· Branch decision, JMP, SZ, SZA, SNZ, SIZ, SDZ,

SIZA, SDZA,CALL,RET, RETI

ProgramMemory

The Program Memory is the location where the user

code or program is stored. The type of memory is the

mask ROM memory. It offer the most cost effective solu-

tionsforhighvolumeproducts.

Structure

The Program Memory has a capacity of 512K by 16,

256K by 16, 128K by 16 or 64K by 16 bits depending

uponwhichdeviceisselected.

SpecialVectors

Within the Program Memory, certain locations are re-

servedforspecialusagesuchasresetandinterrupts.

· Location000H

This vector is reserved for use by the device reset for

program initialization. After a device reset is initiated,

the program will jump to this location and begin execu-

tion.

· Location004H

This vector is used by the external interrupt. If the ex-

ternal interrupt pin on the device goes low, the pro-

gram will jump to this location and begin execution if

the external interrupt is enabled and the stack is not

full.

· Location008H

This vector is reserved for the Timer/Event Counter 0

interrupt service program. If a timer interrupt results

from a Timer/Event Counter 0 overflow, and if the in-

terrupt is enabled and the stack is not full, the program

beginsexecutionatlocation008H.

· Location00CH

This vector is reserved for the Timer/Event Counter 1

interrupt service program. If a timer interrupt results

from a Timer/Event Counter 1 overflow, and if the in-

terrupt is enabled and the stack is not full, the program

beginsexecutionatlocation00CH.

· Location010H

This vector is reserved for the Timer Counter 2 inter-

rupt service program. If a timer interrupt results from a

Timer Counter 2 overflow, and if the interrupt is en-

abled and the stack is not full, the program begins ex-

ecution at location 0010H. Timer 2 Counter overflow

interrupt share with UART interrupt require. Using the

UART interrupt require is defined by enabled UART

functionenableconfigurationoption.

· Location014H

This vector is reserved for the ERCOCI interrupt ser-

vice program. If an external RC oscillation converter

interrupt results from an external RC oscillation con-

verter interrupt is activated, and the stack is not full,

theprogrambeginsexecutionatlocation0014H.

· Location018H

This vector is reserved for the Adpcm interrupt service

program. If a Adpcm interrupt results, and if the inter-

rupt is enabled and the stack is not full, the program

beginsexecutionatlocation0018H.

P r o g r a m C o u n t e r

S t a c k L e v e l 1

S t a c k L e v e l 2

S t a c k L e v e l 3

S t a c k L e v e l 1 2

P r o g r a m

M e m o r y

T o p o f S t a c k

S t a c k

P o i n t e r

B o t t o m o f S t a c k

HT37B90 Datasheet(PDF) 11 Page - Holtek Semiconductor Inc

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