Xerox 550 - Page 93

PSS Operations
PLS Operations
initial TSA -
-
terminal TSA = initial TSA-28
+1
(RO) -27
+2
(R1) -26
+3
(R2)
-25
+4 (R3) -24
+5
(R4) -23
+6 (R5) -22
+7 (R6)
-21
+8
(R7)
-20
+9 (R8)
-19
+10
(R9)
-18
+11
(RlO)
-17
+12 (Rll )
-16
+13 (R12)
-15
+14 (R13)
-14
+15 (R14)
-13
+16 (R15)
-12
+17
-11
+18
-10
+19 -9
+20
-8
+21
-7
+22
-6
+23
-5
+24
+25
(PSW1)
-3
+26
(PSW2)
-2
+27
(PSW3)
t -1
initial TSA
+28 (PSW4)
-
initial TSA
tAs a function of the hardware, the contents of these 8 locations are in-
determinate after a PSS instruction and ignored by a PLS instruction. These
locations are reserved for future enhancements and must not be used.
Figure 12.
Typical 28-Word Portion of Memory Stack for PSS and PLS
86 Push-Down Instructions (Privileged)