Control Data Cyber 170 State Hardware Reference Manual page 162

PP
Central Memory
Access
Instructions
61dm Central read (dl words from (A) to m CRM d,m
PP location 0000 is used by hardware. This instruction disassembles 60-bit
words from central memory into 12-bit words, and places these in consecutive
PP
memory locations, beginning with the leftmost 12 bits of the first 60-bit word.
The parameters of the transfer are as follows: If bit 17 of
A
is 0, A bits 0
through 16 contain the absolute address of the first 60-bit word transferred.
If bit 17 of A is 1, hardware adds relocation register R to zero-extended A
bits 0 through 16 to obtain the absolute address of the first 60-bit word
transferred. For further information, refer to R
Register under Input/Output
Unit in chapter 2, and PP Relocation Register Format under PP Instruction
Descriptions. PP location d must contain the number of 60-bit words
transferred. Field m gives the PP location into which the first 12-bit word
is
placed.
This instruction stores P plus 1 into PP location 0000 before beginning the
transfer. After the transfer is completed, the next instruction is taken from
1 plus whatever address is stored in location 0000. If the transfer overwrites
location 0000, execution resumes at the location specified by (0000) plus 1 and
results are undefined. (PP memory addressing is cyclic, and location 0000
follows location 7777.)
The A register is incremented by 1 after each 60-bit word is read from central
memory. If the incrementing changes A bit 17, the central memory addressing
is
switched between direct address and relocation address modes. Refer to Central
Memory Addressing by PPs in chapter 5.
After the transfer is completed, the
A
register contains either the address of
the last word transferred plus 1 (direct addressing) or the same address Less
the contents of the relacation address register (relocation addressing), except
as follows: If the last word transferred is from a relative address 3777768
and relocation is in effect, then the A register is cleared, and the value
returned in A may not point to the last word transferred plus 1 .