Freescale Semiconductor MC68881 - Source Format Field Encoding

Table 4-14. Source Format Field Encoding
Source Format External Operand Length Allowed
Encoding Data Format in Bytes <ea~
DO0 Long Word Integer 4 Data
001 Single Precision Real 4 Data
010 Extended Precision Real 12 Memory
011 Packed Decimal Real 12 Memory
100 Word Integer 2 Data
101 Double Precision Real 8 Memory
110 Byte Integer 1 Data
The encoding format for this class of instructions is:
15 14 13
1 1 1
0 1 0
12 11 10 9 8 7 6 5 4 3 2 1 0
1 COPROCESSOR ID I 0 { 0 0 } 0 I 0 I 0 I 0 I .0 I 0
t I DESTINATION
111 REGISTER
EXTENSION
The destination register field is encoded as shown in Table 4-12.
The extension field is used as an offset into the FPCP constant ROM. The FMOVECR
instruction definition in 4.6 INDIVIDUAL INSTRUCTION DESCRIPTIONS provides the valid
extension field values for the FMOVECR instruction. The only service required by the FPCP
from the MPU is the passing of the MPU PC to FPIAR if exceptions (other than BSUN) are
enabled. This service is requested with the null (CA= 1, PC= 1) primitive.
4.7.1.4 MOVE TO EXTERNAL DESTINATION INSTRUCTIONS. External destinations are
either memory or an MPU data register. Data format conversion from the extended data
format to one of the seven memory data formats is implicit for these instructions. The
encoding format for this class of instructions is:
15 14 13 12 11 10 .9 8 7 6 5 4 3 2 1 0
COPROCESSOR EFFECTIVF 7 ADDRESS
1 1 1 1 ID 0 0 0 MOD E , | REGISTER
DESTINATION SOURCE EXTENSION
0 1 I FORMAT REGISTER
The source register field is encoded as shown in Table 4-12.
The destination format field indicates the data format of the external destination. The MPU
performs all transfers to an external destination at the request of the FPCP. When the FPCP
MC68881/MC68882 USER'S MANUAL FREESCALE
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