LH79524/LH79525 User’s Guide
External Memory Controller
Version 1.0
7-47
7.5.2.18 Static Memory Extended Wait Register (WAIT)
The Static Memory Extended Wait Register is used to time long static memory read and
write transfers (longer than can be supported by the SWAITRD or SWAITWR registers)
when the EW bit of the SCONFIG register is enabled. There is only a single WAIT register.
These registers should 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.
However, if necessary, these control bits
can be altered during normal operation.
Table 7-45. WAIT Register
BIT
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
FIELD
///
RESET
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
TYPE
RO
RO
RO
RO
RO
RO
RO
RO
RO
RO
RO
RO
RO
RO
RO
RO
BIT
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
FIELD
///
WAIT
RESET
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
TYPE
RO
RO
RO
RO
RO
RO
RW
RW
RW
RW
RW
RW
RW
RW
RW
RW
ADDR
0xFF 0x080
Table 7-46. WAIT Fields
BITS
NAME
FUNCTION
31:10
///
Reserved
Reading returns 0. Write the reset value.
9:0
WAIT
External Wait Time Out
Wait Time Out = (WAIT+1) x 16 HCLK clock periods