PIC18F4520ESLASHMLQTP datasheet(313/390 Pages) MICROCHIP

313 / 390 page

 2004 Microchip Technology Inc.

Preliminary

DS39631A-page 311

PIC18F2420/2520/4420/4520

CALLW

Subroutine Call Using WREG

Syntax:

CALLW

Operands:

None

Operation:

(PC + 2)

→ TOS,

(W)

→ PCL,

(PCLATH)

→ PCH,

(PCLATU)

→ PCU

Status Affected:

None

Encoding:

0000

0001

0100

Description

First, the return address (PC + 2) is

pushed onto the return stack. Next, the

contents of W are written to PCL; the

existing value is discarded. Then, the

contents of PCLATH and PCLATU are

latched into PCH and PCU,

respectively. The second cycle is

executed as a NOP instruction while the

new next instruction is fetched.

Unlike CALL, there is no option to

update W, Status or BSR.

Words:

Cycles:

Q Cycle Activity:

Decode

Read

WREG

PUSH PC to

stack

operation

Example:

HERE

CALLW

Before Instruction

address (HERE)

PCLATH =

10h

PCLATU =

00h

06h

After Instruction

001006h

TOS

address (HERE + 2)

PCLATH =

10h

PCLATU =

00h

06h

MOVSF

Move Indexed to f

Syntax:

MOVSF [zs], fd

Operands:

≤ zs ≤ 127

≤ fd ≤ 4095

Operation:

((FSR2) + zs) → fd

Status Affected:

None

Encoding:

1st word (source)

2nd word (destin.)

1110

1111

1011

ffff

0zzz

ffff

zzzzs

ffffd

Description:

The contents of the source register are

moved to destination register ‘fd’. The

actual address of the source register is

determined by adding the 7-bit literal

offset ‘zs’ in the first word to the value of

FSR2. The address of the destination

‘fd’ in the second word. Both addresses

can be anywhere in the 4096-byte data

space (000h to FFFh).

The MOVSF instruction cannot use the

PCL, TOSU, TOSH or TOSL as the

destination register.

If the resultant source address points to

an indirect addressing register, the

value returned will be 00h.

Words:

Cycles:

Q Cycle Activity:

Decode

Determine

source addr

Determine

source addr

Read

source reg

Decode

operation

No dummy

read

operation

Write

(dest)

Example:

MOVSF

[05h], REG2

Before Instruction

FSR2

80h

Contents

of 85h

33h

REG2

11h

After Instruction

FSR2

80h

Contents

of 85h

33h

REG2

33h

PIC18F4520E/MLQTP Datasheet(PDF) 313 Page - Microchip Technology

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