Computer Hardware User's Guide

CALLcond Call Subroutine Conditionally
13-86
Syntax CALL cond src
Operation If cond is true:
Next PC → *++SP
If src is in register addressing mode (R n , 0 ≤ n ≤ 27),
src → PC.
If src is in PC-relative mode (label or address),
displacement + PC + 1 → PC.
Else, continue
Operands
src conditional-branch addressing modes (B):
0 register
1 PC relative
Opcode
31 24 23 16 8 7 015
01110 B
0 Register or displacement cond 0000
Description A call is performed if the condition is true. If the condition is true, the next PC
value is pushed onto the system stack. If the
src operand is expressed in regis-
ter addressing mode, the contents of the specified register are loaded into the
PC. If the src operand is expressed in PC-relative mode, the assembler gener-
ates a displacement: displacement = label – (PC of call instruction + 1). This
displacement is stored as a 16-bit signed integer in the 16 LSBs of the call in-
struction word. This displacement is added to the PC of the call instruction plus
1 to generate the new PC. This instruction flushes the pipeline as shown in
Example 8–13 on page 8-18.
The ’C3x provides 20 condition codes that can be used with this instruction
(see Table 13–12 on page 13-30 for a list of condition mnemonics, condition
codes, and flags). Condition flags are set on a previous instruction only when
the destination register is one of the extended-precision registers (R7–R0) or
when one of the compare instructions (CMPF, CMPF3, CMPI, CMPI3, TSTB,
or TSTB3) is executed.
Cycles 5
Status Bits LUF Unaffected
LV Unaffected
UF Unaffected
N Unaffected
Z Unaffected
V Unaffected
C Unaffected
OVM Operation is not affected by OVM bit value.
Mode Bit