The address pointer is apparently a straight line, but actually it is calculated every 1 Fs cycle, so draw a staircase-like locus as shown in Figure 4.21. This step becomes the internally generated value of PG.
Figure 4.21 Enlarged view of address pointer output
When the frequency is increased, the PG generation value increases, so the PG output and address pointer output values (functions) have a steep slope.
Conversely, when the frequency is lowered, the PG generation value decreases, so the PG output value and the address pointer output value have a gentle slope as shown in Figure 4.22.