HT46R232 datasheet(7/50 Pages) HOLTEK

7 / 50 page

HT46R232/HT46C232

Rev. 1.40

November 23, 2005

Program Memory - EPROM

The program memory (EPROM) is used to store the pro-

gram instructions which are to be executed. It also con-

tains data, table, and interrupt entries, and is organized

into 4096

´16 bits which are addressed by the program

counter and table pointer.

Certain locations in the ROM are reserved for special

usage:

· Location 000H

Location 000H is reserved for program initialization.

After chip reset, the program always begins execution

at this location.

· Location 004H

Location 004H is reserved for the external interrupt

service program. If the INT input pin is activated, and

the interrupt is enabled, and the stack is not full, the

program begins execution at location 004H.

· Location 008H

Location 008H is reserved for the Timer/Event Coun-

ter 0 interrupt service program. If a timer interrupt re-

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

interrupt is enabled and the stack is not full, the pro-

gram begins execution at location 008H.

· Location 00CH

Location 00CH is reserved for the Timer/Event Coun-

ter 1 interrupt service program. If a timer interrupt re-

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

interrupt is enabled and the stack is not full, the pro-

gram begins execution at location 00CH.

· Location 010H

Location 010H is reserved for the A/D converter inter-

rupt service program. If an A/D converter interrupt re-

sults from an end of A/D conversion, and if the

interrupt is enabled and the stack is not full, the pro-

gram begins execution at location 010H.

· Location 014H

This area is reserved for the I

2C Bus interrupt service

program. If the I

2C Bus interrupt resulting from a slave

address is match or completed one byte of data trans-

fer, and if the interrupt is enable and the stack is not

full, the program begins execution at location 014H.

· Table location

Any location in the ROM can be used as a look-up ta-

ble. The instructions

²TABRDC [m]² (the current page,

page=256 words) and

²TABRDL [m]² (the last page)

transfer the contents of the lower-order byte to the

specified data memory, and the contents of the

higher-order byte to TBLH (Table Higher-order byte

byte in the table is well-defined; the other bits of the ta-

ble word are all transferred to the lower portion of

TBLH. The TBLH is read only, and the table pointer

(TBLP) is a read/write register (07H), indicating the ta-

ble location. Before accessing the table, the location

should be placed in TBLP. All the table related instruc-

tions require 2 cycles to complete the operation.

These areas may function as a normal ROM depend-

ing upon the users requirements

Stack Register - STACK

This is a special part of the memory which is used to

save the contents of the program counter only. The

stack is organized into 8 levels and is neither part of the

data nor part of the program space, and is neither read-

able nor writeable. The activated level is indexed by the

stack pointer (SP) and is neither readable nor writeable.

At the state of a subroutine call or an interrupt acknowl-

edgment, the contents of the program counter are

pushed onto the stack. At the end of the subroutine or an

interrupt routine, signaled by a return instruction (RET or

RETI), the program counter is restored to its previous

P r o g r a m

M e m o r y

D e v i c e I n i t i a l i z a t i o n P r o g r a m

E x t e r n a l I n t e r r u p t S u b r o u t i n e

T i m e r / E v e n t C o u n t e r 0 I n t e r r u p t S u b r o u t i n e

L o o k - u p T a b l e ( 2 5 6 w o r d s )

N o t e : n r a n g e s f r o m 0 t o F

A / D C o n v e r t e r I n t e r r u p t

I 2 C B u s I n t e r r u p t

F F F H

n F F H

T i m e r / E v e n t C o u n t e r 1 I n t e r r u p t S u b r o u t i n e

F 0 0 H

1 6 b i t s

0 0 0 H

0 0 4 H

0 0 8 H

0 0 C H

0 1 0 H

0 1 4 H

n 0 0 H

Program Memory

Instruction

Table Location

*11

*10

TABRDC [m]

P11

P10

TABRDL [m]

1111

Table Location

Note: *11~*0: Table location bits

P11~P8: Current program counter bits

@7~@0: Table pointer bits

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