Mnemonic
SRA 
Description
The contents of the accumulator are shifted right, a bit at a time. Zeros (one for each rightshifted bit) are shifted into accumulator bitposition 0, regardless of the initial value of bitposition 0. Bits are shifted out of accumulatorposition 15 and lost. An example of a right shift of two positions is:
The number of positions shifted is specified by a shift count. Location of the shift count is determined by the T bits in the instruction:
T Bits (6 and 7)  Shift Count Location  

00  Loworder six bits of displacement (in the shift instruction)  
01  Loworder six bits in indexregister 1  
10  Loworder six bits in indexregister 2  
11  Loworder six bits in indexregister 3 
A value must be put into the shiftcount location before the operation is started. The operation is ended when the specified number of shifts have been performed. The shift count, however, need be set up only once. After the operation is ended, the original shift count (for example, a count in indexregister 1) is the same as its initial value. (Decrementing of the count is performed in separate circuits.)
The maximum shift count that can be specified is 63 (111111 in binary). A rightshift of sixteen, however, puts zeros in all positions of the accumulator.
A shift count of zero (000000 in binary) causes this instruction to perform as a nooperation: contents of the accumulator remain unchanged.
Core storage is not addressed during execution of the shiftrightaccumulator instruction.
Indicators: The carry and overflow indicators are not affected during execution of the SRA operation.
Examples
Shift Left Accumulator/No Operation
Assembler Language Coding  Hexadecimal Value  Description of Instruction  

Label  Operation  F  T  


32  33  35..40..  
SRA  DISP  18*X  Contents of A shift right the number of shift counts in DISP  
SRA  1  1900  Contents of A shift right the number of shift counts in XR1  
SRA  2  1A00  Contents of A shift right the number of shift counts in XR2  
SRA  3  1B00  Contents of A shift right the number of shift counts in XR3 
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