Mnemonic
SRT 
Description
The contents of the accumulator and accumulator extension are shifted right, a bit at a time, as if these two registers made up a single 32bit register. Bits shifted out of extensionposition 15 are lost.
Bits shifted in the highorder end (bit 0) of the accumulator are the same value as the original sign bit (that is, the value of the bit in position 0 at the start of the operation). This type of shifting is called arithmetic shifting. An example of a right shift of two positions of a negative number 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 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 32 propagates the sign bit from accumulatorposition 0 into all positions of the accumulator and the accumulator extension.
A shift count of zero (000000 in binary) causes this instruction to perform as a nooperation: contents of the accumulator and extension remain unchanged.
Core storage is not addressed during execution of the shiftrightaccumulatorandextension instruction.
Indicators: The carry and overflow indicators are not affected during execution of the SRT instruction.
Examples
Shift Left Accumulator and Extension
Assembler Language Coding  Hexadecimal Value  Description of Instruction  

Label  Operation  F  T  


32  33  35..40..  
SRT  DISP  18*X  Contents of A and Q shift right the number of shift counts in DISP  
SRT  1  1980  Contents of A and Q shift right the number of shift counts in XR1  
SRT  2  1A80  Contents of A and Q shift right the number of shift counts in XR2  
SRT  3  1B80  Contents of A and Q shift right the number of shift counts in XR3 
But wait, there's MORE...