Motorola MC68VZ328 - Manual (Page 123)

Programming Model
DRAM Controller 7-13
The REF value is the time of 1 refresh cycle.
Example 7-1. Calculating REF Field Values for Refresh Times
When CLK = 0, 32 kHz (or 34.8 kHz) is used for refresh control.
• If REF = 0, the refresh rate = 2 × 32 kHz.
• If REF = 1, the refresh rate = 32 kHz.
• If REF = (2 to 15), the refresh rate = 32 kHz / (REF + 1).
When CLK = 1, the system clock is used for refresh control.
• The refresh rate = SYSCLK / (32 × (REF + 1)).
REF
Bits 4–0 Refresh Cycle—This value determines the refresh rate for
the DRAM controller. The refresh rate can be calculated
using the equation shown in Example 7-1. See description
Table 7-6. DRAM Memory Configuration Register Description (Continued)
Name Description Setting