PIC17LC42A datasheet(37/240 Pages) MICROCHIP

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DS30412C-page 37

PIC17C4X

6.2.2.2

CPU STATUS REGISTER (CPUSTA)

The CPUSTA register contains the status and control

bits for the CPU. This register is used to globally

enable/disable interrupts. If only a speciﬁc interrupt is

desired to be enabled/disabled, please refer to the

INTerrupt STAtus (INTSTA) register and the Peripheral

Interrupt Enable (PIE) register. This register also indi-

cates if the stack is available and contains the

Power-down (PD) and Time-out (TO) bits. The TO, PD,

and STKAV bits are not writable. These bits are set and

cleared according to device logic. Therefore, the result

of an instruction with the CPUSTA register as destina-

tion may be different than intended.

FIGURE 6-8:

CPUSTA REGISTER (ADDRESS: 06h, UNBANKED)

U - 0

R - 1

R/W - 1

R - 1

U - 0

—

STKAV GLINTD

—

R = Readable bit

W = Writable bit

U = Unimplemented bit,

Read as ‘0’

- n = Value at POR reset

bit7

bit0

bit 7-6:

Unimplemented: Read as '0'

bit 5:

STKAV: Stack Available bit

This bit indicates that the 4-bit stack pointer value is Fh, or has rolled over from Fh

→ 0h (stack overﬂow).

1 = Stack is available

0 = Stack is full, or a stack overﬂow may have occurred (Once this bit has been cleared by a

stack overﬂow, only a device reset will set this bit)

bit 4:

GLINTD: Global Interrupt Disable bit

This bit disables all interrupts. When enabling interrupts, only the sources with their enable bits set can

cause an interrupt.

1 = Disable all interrupts

0 = Enables all un-masked interrupts

bit 3:

TO: WDT Time-out Status bit

1 = After power-up or by a CLRWDT instruction

0 = A Watchdog Timer time-out occurred

bit 2:

PD: Power-down Status bit

1 = After power-up or by the CLRWDT instruction

0 = By execution of the SLEEP instruction

bit 1-0:

Unimplemented: Read as '0'

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