Maxim-integrated MAXQ610 Manual de usuario descargar pdf (Pagina 172)

14-5

MAXQ610 User’s Guide

{L/S}CALL src {Long/Short} Call to Subroutine

Description:

Performs a call to the subroutine destination specified by src

. The CALL instruction uses an 8-bit

immediate src to perform a relative short call (IP +127/-128 words). The CALL instruction uses a

16-bit immediate src to perform an absolute long CALL

to the specified 16-bit address. The PFX[0]

Using the optional ‘L’ prefix (i.e., LCALL) will result in an absolute long call and use of the PFX[0]

will be flagged by the assembler if the destination is out or range. Specifying an internal register

src (no matter whether 8-bit or 16-bit) always produces an absolute CALL to a 16-bit address, thus

the ‘L’ and ‘S’ prefixes should not be used. The PFX[n] register value is used to supply the high

address byte when an 8-bit register src is specified.

Status Flags:

None

Operation:

@++SP ← IP + 1

PUSH

IP ← src

Absolute CALL

IP ← IP + src

Relative CALL

Encoding:

f011

1101 ssss ssss

Example(s):

CALL label1 ; relative call to label1 (must be within

; IP +127/-128 address range)

CALL label1 ; absolute call to label1 = 0120h

; MOVE PFX[0], #01h

; CALL #20h.

CALL DP[0] ; DP[0] holds 16-bit address of subroutine

CALL M0[0] ; assume M0[0] is an 8-bit register

; absolute call to addr16

; high(addr16)=00h (PFX[0])

; low (addr16)=M0[0]

MOVE PFX[0], #22h ;

CALL M0[0] ; assume M0[0] is an 8-bit register

; high(addr16)=22h (PFX[0])

; low (addr16)=M0[0]

LCALL label1 ; label=0120h and is relative to this instruction

; absolute call is forced by use of ‘L’ prefix

; MOVE PFX[0], #01h

; CALL #20h

SCALL label1 ; relative offset for label1 calculated and used

; if label1 is not relative, assembler will generate an

; error

SCALL #10h ; relative offset of #10h is used directly by the CALL

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