Page 12 - DCAP507_SYSTEM_SOFTWARE

System Software

Notes  Contents of status word register
Bit position Field name Use
0 MODE 0=user mode, 1=supervisor mode
1 IDLE 0=running, 1=idle
2~5 ID Process identifier
6~7 CC Condition code
8~11 MASK Interrupt mask
12~15 Unused
16~23 ICODE Interruption code

1.2.4 SIC/XE Machine Architecture

 Memory
 Almost the similar as formerly described for SIC
 However 1 MB( 220 bytes)
 More Registers

Mnemonic Number Special use
B 3 Base register; used for addressing

S 4 General working register
T 5 General working register
F 6 Floating-point acumulator (48bits)

 Data Formats
 Floating-point data type: frac*2(exp-1024)
 frac: 0~1

 exp: 0~2047
 Instruction Formats
Format 1
op(8)
Format 2
op(8) r1(4) r2(4)

Format 3 e=0
op(6) n I x b p e disp(12)

Format 4 e =1
op(6) n I x b p e Address(20)

6 LOVELY PROFESSIONAL UNIVERSITY