EM78P259N/260N

8-Bit Microprocessor with OTP ROM

6.2 Special Purpose Registers

6.2.1 A (Accumulator)

Internal data transfer operation, or instruction operand holding usually involves the temporary storage function of the Accumulator, which is not an addressable register.

6.2.2 CONT (Control Register)

Bit 7

 

Bit 6

 

Bit 5

 

Bit 4

 

Bit 3

 

Bit 2

 

Bit 1

 

Bit 0

 

 

 

 

 

 

 

INTE

 

INT

 

TS

 

TE

 

PSTE

 

PST2

 

PST1

 

PST0

 

 

 

 

 

 

 

 

 

 

 

 

Note: The CONT register is both readable and writable

 

 

 

 

 

 

 

Bit 6 is read only.

 

 

 

 

 

 

 

 

 

 

 

Bit 7 (INTE): INT signal edge

 

 

 

 

 

 

 

 

 

 

 

0

= interrupt occurs at the rising edge on the INT pin

 

 

 

 

 

1

= interrupt occurs at the falling edge on the INT pin

 

Bit 6 (INT):

Interrupt enable flag

 

 

 

 

 

 

 

 

 

 

 

0

= masked by DISI or hardware interrupt

 

 

 

 

 

 

 

1

= enabled by the ENI/RETI instructions

 

 

 

 

 

 

 

This bit is readable only.

 

 

 

 

 

 

 

Bit 5 (TS):

TCC signal source

 

 

 

 

 

 

 

 

 

 

 

0

= internal instruction cycle clock. P54 is bi-directional I/O pin.

 

 

 

1

= transition on the TCC pin

 

 

 

 

 

 

 

Bit 4 (TE):

TCC signal edge

 

 

 

 

 

 

 

 

 

 

 

0

= increment if the transition from low to high takes place on the TCC

 

 

 

pin

 

 

 

 

 

 

 

 

 

 

 

 

 

1

= increment if the transition from high to low takes place on the TCC

 

 

 

pin.

 

 

 

 

 

 

 

 

 

 

 

Bit 3 (PSTE): Prescaler enable bit for TCC

 

 

 

 

 

 

 

 

 

0

= prescaler disable bit. TCC rate is 1:1.

 

 

 

 

 

 

 

1

= prescaler enable bit. TCC rate is set as Bit 2 ~ Bit 0.

 

Product Specification (V1.2) 05.18.2007

• 15

(This specification is subject to change without further notice)

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IBM EM78P259N/260N manual Special Purpose Registers, Accumulator, Control Register