HT36B2 datasheet(7/39 Pages) HOLTEK

7 / 39 page

HT36B2

Rev. 1.10

March 10, 2005

Program ROM

HT36B2 provides 17 address lines W A16~0 to read the

Program ROM which is up to 2M bits, and is comm only

used for the wavetable voice codes and the program

memory. It provides two address types, one type is for

program ROM, which is addressed by a bank pointer

PF3~0 and a 13-bit program counter PC 12~0; and the

other type is for wavetable code, which is addressed by

the start address ST15~0. On the program type,

WA16~0= PF3~0

´ 213+ PC12~0. On the wavetable

ROM type, WA16~0=ST15~0

´ 25.

Program Memory

- ROM

The program memory is used to store the program in-

structions which are to be executed. It also contains

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

8192

´16 bits, addressed by the bank pointer, program

counter and table pointer.

Certain locations in the program memory of each bank

are reserved for special usage:

· Location 000H on bank0

This area is reserved for the initialization program. Af-

ter a chip reset, the program always begins execution

at location 000H on bank0.

· Location 008H

This area is reserved for the Timer/Event Counter 0 in-

terrupt service program on each bank. If timer interrupt

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

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

begins execution at location 008H corresponding to its

bank.

· Location 00CH

This area is reserved for the Timer/Event Counter 1

interrupt service program on each bank. If a timer in-

terrupt results from a Timer/Event Counter 1 overflow,

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

the program begins execution at location 00CH corre-

sponding to its bank.

· Table location

Any location in the ROM space can be used as

look-up tables. The instructions TABRDC[m] (the cur-

rent page, 1 page=256 words) and TABRDL [m] (the

last page) transfer the contents of the lower-order

byte to the specified data memory, and the

higher-order byte to TBLH (08H). Only the destination

of the lower-order byte in the table is well-defined, the

higher-order byte of the table word are transferred to

the TBLH. The Table Higher-order byte register

(TBLH) is read only. The Table Pointer (TBLP) is a

read/write register (07H), which indicates the table lo-

cation. Before accessing the table, the location must

be placed in TBLP. The TBLH is read only and cannot

be restored. If the main routine and the ISR (Interrupt

Service Routine) both employ the table read instruc-

tion, the contents of the TBLH in the main routine are

likely to be changed by the table read instruction used

in the ISR. Errors can occur. In this case, using the ta-

ble read instruction in the main routine and the ISR si-

multaneously should be avoided. However, if the table

read instruction has to be applied in both the main rou-

tine and the ISR, the interrupt should be disabled prior

to the table read instruction. It will not be enabled until

the TBLH has been backed up. All table related in-

structions need two cycles to complete the operation.

These areas may function as normal program mem-

ory depending upon user requirements.

· Bank pointer

The program memory is organized into 16 banks and

each bank into 8192

´16 bits of program ROM. PF3~0

is used as the ROM bank pointer. After an instruction

has been executed to write data to the PF register to

select a different bank, note that the new bank will not

be selected immediately. It is not until the following in-

struction has completed execution that the bank will

be actually selected.

Instruction(s)

Table Location

*16

*15

*14

*13

*12

*11

*10

TABRDC [m]

P16 P15 P14 P13 P12 P11 P10

TABRDL [m]

P16 P15 P14 P13

11111

Table Location

Note:

*12~*0: Table location bits

@7~@0: Table pointer bits

P12~P8: Current Program Counter bits

P16~P13: Bits of bank PF3~PF0

0 0 0 0 H

0 0 0 8 H

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

P r o g r a m

R O M

1 6 b i t s

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

n 0 0 H

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

1 F F F H

N o t e : n r a n g e s f r o m 0 0 t o 1 F .

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

0 0 0 C H

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

Program Memory for Each Bank

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