Maxim Integrated DS4830A Optical Microcontroller User Manual
Page 206
DS4830A User’s Guide
206
{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) will result in
an absolute long call and use of the PFX[0] register. Using the optional ‘S’ prefix (i.e.
SCALL) will attempt to generate a relative short call, but 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:
15
0
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