HT48CA3 Holtek Semiconductor Inc, HT48CA3 Datasheet - Page 6

• Manufacturer Part Number: HT48CA3
• Description: 8-Bit Remote Type MCU
• Manufacturer: Holtek Semiconductor Inc

sequently executed, stack overflow occurs and the first
entry will be lost (only the most recent 8 return ad-
dresses are stored).
Data Memory - RAM
The data memory is designed with 250 8 bits. The
data memory is divided into two functional groups: spe-
cial function registers and general purpose data mem-
ory (224 8). Most are read/write, but some are read
only.
The special function registers include the indirect ad-
dressing registers (R0;00H, R1;02H) bank pointer
(BP;04H), Timer/Event Counter 0 (TMR0;0DH),
Timer/Event Counter 0 control register (TMR0C;0EH),
Timer/Event Counter 1 higher order byte register
(TMR1H;0FH), Timer/Event Counter 1 lower order byte
register (TMR1L;10H), Timer/Event Counter 1 control
register (TMR1C;11H), program counter lower-order
byte register (PCL;06H), memory pointer registers
(MP0;01H, MP1;03H), accumulator (ACC;05H), table
pointer (TBLP;07H, TBHP;1FH), table higher-order
b y t e r e g i s t e r ( T B L H ; 0 8 H ) , s t a t u s r e g i s t e r
(STATUS;0AH), interrupt control register (INTC;0BH),
Watchdog Timer option setting register (WDTS;09H),
I/O registers (PA;12H, PB;14H, PC;16H, PF;1CH, and
I/O control registers (PAC;13H, PBC;15H, PCC;17H,
PFC;1DH). The remaining space before the 20H is re-
served for future expanded usage and reading these
locations will get 00H . The general purpose data
memory, addressed from 20H to FFH, is used for data
and control information under instruction commands.
All of the data memory areas can handle arithmetic,
logic, increment, decrement and rotate operations di-
rectly. Except for some dedicated bits, each bit in the
data memory can be set and reset by SET [m].i and
memory pointer registers (MP0 or MP1).
Indirect Addressing Register
Location 00H and 02H are indirect addressing registers
that are not physically implemented. Any read/write op-
eration of [00H] ([02H]) will access data memory pointed
to by MP0 (MP1). Reading location 00H (02H) itself indi-
rectly will return the result 00H. Writing indirectly results
in no operation.
The memory pointer registers (MP0 and MP1) are 8-bit
registers.
Accumulator
The accumulator is closely related to ALU operations. It
is also mapped to location of the data memory and can
carry out immediate data operations. The data move-
ment between two data memory locations must pass
through the accumulator.
Rev. 1.40
CLR [m].i . They are also indirectly accessible through
6
Arithmetic and Logic Unit - ALU
This circuit performs 8-bit arithmetic and logic opera-
tions. The ALU provides the following functions:
The ALU not only saves the results of a data operation
but also changes the status register.
Arithmetic operations (ADD, ADC, SUB, SBC, DAA)
Logic operations (AND, OR, XOR, CPL)
Increment and decrement (INC, DEC)
Rotation (RL, RR, RLC, RRC)
Increment and Decrement (INC, DEC)
Branch decision (SZ, SNZ, SIZ, SDZ ....)
RAM mapping
HT48CA3
July 16, 2003