Table 7-23. Precharge Register; Table 7-24. Precharge Fields; Dynamic Precharge Command Period Register (Precharge) - Sharp LH79524 User Manual

External Memory Controller

7.5.2.7 Dynamic Precharge Command Period Register (PRECHARGE)

The Dynamic Memory Precharge Command Period Register programs the Precharge
Command Period, tRP. This value is normally found in SDRAM data sheets as tRP.
This register must only be modified during system initialization, or when there are
no current or outstanding transactions. Software can ensure that there are no current or
outstanding transactions by waiting until the memory controller is idle, then entering
Low-Power Mode (CONTROL:MODE = 1), or Disable Mode (CONTROL:ENABLE = 0).
When in these two modes, external memory access is not allowed, ensuring that
changing parameters will not corrupt external data. Low-Power Mode automatically
refreshes SDRAM; Disable Mode requires commanding the SDRAM to Self Refresh
(DYNMCTRL:SR = 1) prior to entering Disable.
BIT
FIELD
RESET
TYPE
BIT
FIELD
RESET
TYPE
ADDR
BITS
31:4
3:0
7-36

Table 7-23. PRECHARGE Register

31 30 29 28 27
0 0 0 0 0
RO RO RO RO RO
15 14 13 12 11
0 0 0 0 0
RO RO RO RO RO

Table 7-24. PRECHARGE Fields

NAME
///
Reserved Reading returns 0. Write the reset value.
Precharge Command Period
tRP
Period = (tRP + 1) External Memory Clock periods
26 25 24 23
///
0 0 0 0
RO RO RO RO
10 9 8 7
///
0 0 0 0
RO RO RO RO
0xFFFF1000 + 0x030
FUNCTION
Version 1.0
LH79524/LH79525 User's Guide
22 21 20 19 18
0 0 0 0 0
RO RO RO RO RO
6 5 4 3 2
0 0 0 1 1
RO RO RO RW RW
17 16
0 0
RO RO
1 0
tRP
1 1
RW RW