MOTOROLA M68040 USER’S MANUAL 9- 43
FPTS, FPTE, FPTM—Collectively, these fields are referred to as the FPTEMP register
and normally contain the destination operand for dyadic operations converted to extended
precision. If the instruction specifies a packed decimal real source, bits 95–64 of the
operand reside in FPTM [31–00], and the FPTS, FPTE, and FPTM [63–32] fields are
OPCLASS—This field refers to bits 15–13 of CMDREG1B. Note that CMDREG1B is
identical to the second word of a floating-point arithmetic instruction opcode.
STAG, DTAG—These 3-bit fields specify the data type of the source and destination
operands, respectively. STAG is undefined for a packed decimal real source operand. The
encodings for STAG and DTAG are as follows:
000 = Normalized
001 = Zero
010 = Infinity
011 = NAN
100 = Extended-Precision Denormalized or Unnormalized Input
101 = Single- or Double-Precision Denormalized Input
T—If set, this bit indicates that a post-instruction exception has occurred. Since only an
opclass 3 instruction can indicate a post-instruction exception, this bit indicates that the
exception is caused by an FMOVE OUT instruction.
WBTS, WBTE [15,14–00], WBTM [66,65–02,01,00], SBIT—These fields contain the
exception operand in internal data format for E3 exceptions. Collectively, these fields are
called the WBTEMP and are an image of the intermediate result. WBTM66 is the overflow
bit; WBTM1, WBTM0, and SBIT are the guard, round, and sticky bits, respectively.