Maxim Integrated MAXQ7666 - Manual (Page 344)

MAXQ7665/MAXQ7666 User’s Guide
14-7
{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] register is used to supply the high byte of a 16-bit
immediate address for the absolute long CALL. Using the optional 'L' prefix (i.e., LCALL) results in an absolute long
call and use of the PFX[0] register. Using the optional 'S' prefix (i.e., SCALL) attempts to generate a relative short call,
but is flagged by the assembler if the destination is out of 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: 15 0
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
f011 1101 ssss ssss
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