EM78P257 datasheet(10/91 Pages) EMC

10 / 91 page

EM78P257

OTP ROM

This specification is subject to change without prior notice.

07.27.2004 (V1.4)

4. FUNCTION DESCRIPTION

DATA & CONTROL BUS

Oscillator Timing

Control

WDT timer

Prescaler

RAM

R1(TCC)

Interrupt

controller

ROM

Instruction

ALU

ACC

Instruction

decoder

OSCI

OSCO /RESET

TCC

/INT

IOC5

COUNTER

STACK 6

IOC6/7

R6/7

PORT5

I/O

P60/INT

P61/CIN3-/TCC1

P62/CIN3+

P63/CO3

P64/CO4

P65/CIN4+

P66/CIN4-/TCC2

P67/IR OUT

P70/OSCO

P71//RESET

TCC4/CIN1+/P50

TCC3/CO1/P51

CO2/P52

CIN2+/P53

TCC/CIN2-/P54

OSCI/CIN1-/P55

TCC5/P56

TCC6/P57

STACK 7

STACK 5

STACK 4

STACK 3

STACK 2

STACK 1

STACK 0

Built-in

OSC

I/O

PORT6/7

Comparator

Fig. 3 Functional block diagram

4.1 Operational Registers

1. R0 (Indirect Addressing Register)

R0 is not a physically implemented register. Its major function is to be an indirect addressing pointer. Any instruction using

R0 as a pointer actually accesses data pointed by the RAM Select Register (R4).

2. R1 (Time Clock /Counter)/TCC

• Increased by an external signal edge which is defined by the TE bit (CONT-4) through the TCC pin,

or by the instruction cycle clock.

• Writable and readable as any other registers.

• The prescaler (RC) is assigned to TCC.

• The contents of the prescaler counter is cleared only when a value is written to TCC register.

3. R2 (Program Counter) & Stack/PC

EM78P257 Datasheet(PDF) 10 Page - ELAN Microelectronics Corp

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