PIC18F4520ESLASHMLQTP datasheet(284/390 Pages) MICROCHIP

284 / 390 page

PIC18F2420/2520/4420/4520

DS39631A-page 282

Preliminary

 2004 Microchip Technology Inc.

Branch if Zero

Syntax:

Operands:

-128

≤ n ≤ 127

Operation:

if ZERO bit is ‘1’

(PC) + 2 + 2n

→ PC

Status Affected:

None

Encoding:

1110

0000

nnnn

Description:

If the ZERO bit is ‘1’, then the program

will branch.

The 2’s complement number ‘2n’ is

added to the PC. Since the PC will

have incremented to fetch the next

instruction, the new address will be

PC + 2 + 2n. This instruction is then a

two-cycle instruction.

Words:

Cycles:

1(2)

Q Cycle Activity:

If Jump:

Decode

Read literal

‘n’

Process

Data

Write to PC

operation

If No Jump:

Decode

Read literal

‘n’

Process

Data

operation

Example:

HERE

Jump

Before Instruction

address (HERE)

After Instruction

If ZERO

address (Jump)

If ZERO

address (HERE + 2)

CALL

Subroutine Call

Syntax:

CALL k {,s}

Operands:

≤ k ≤ 1048575

∈ [0,1]

Operation:

(PC) + 4

→ TOS,

→ PC<20:1>,

if s = 1

(W)

→ WS,

(Status)

→ STATUSS,

(BSR)

→ BSRS

Status Affected:

None

Encoding:

1st word (k<7:0>)

2nd word(k<19:8>)

1110

1111

110s

k19kkk

k7kkk

kkkk

kkkk0

kkkk8

Description:

Subroutine call of entire 2-Mbyte

memory range. First, return address

(PC + 4) is pushed onto the return

stack. If ‘s’ = 1, the W, Status and BSR

registers are also pushed into their

respective shadow registers, WS,

STATUSS and BSRS. If ‘s’ = 0, no

update occurs (default). Then, the

20-bit value ‘k’ is loaded into PC<20:1>.

CALL

is a two-cycle instruction.

Words:

Cycles:

Q Cycle Activity:

Decode

Read literal

‘k’<7:0>,

PUSH PC to

stack

Read literal

‘k’<19:8>,

Write to PC

operation

Example:

HERE

CALL

THERE, 1

Before Instruction

address (HERE)

After Instruction

address (THERE)

TOS

address (HERE + 4)

BSRS

BSR

STATUSS =

Status

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