7.3 Operation
7.3.1 Overview
One of three functions can be selected for the H8/3048 Series refresh controller: interfacing to
DRAM connected to area 3, interfacing to pseudo-static RAM connected to area 3, or interval
timing. Table 7-3 summarizes the register settings when these three functions are used.
Table 7-3 Refresh Controller Settings
Usage
Register Settings
DRAM Interface
PSRAM Interface
Interval Timer
RFSHCR
SRFMD
Selects self-refresh mode
Cleared to 0
PSRAME
Cleared to 0
Set to 1
Cleared to 0
DRAME
Set to 1
Cleared to 0
Cleared to 0
CAS/
WE
Selects 2
CAS
or —
—
2
WE
mode
M9/
M8
Selects column
—
—
addressing mode
RFSHE
Selects
RFSH
signal output
Cleared to 0
RCYCE
Selects insertion of refresh cycles
—
RTCOR
Refresh interval setting
Interrupt interval setting
RTMCSR
CKS2 to CKS0
CMF
Set to 1 when RTCNT = RTCOR
CMIE
Cleared to 0
Enables or disables
interrupt requests
P8DDR
P8
1
DDR
Set to 1 (CS
3
output)
Set to 0 or 1
ABWCR
ABW3
Cleared to 0
—
—
DRAM Interface: To set up area 3 for connection to 16-bit-wide DRAM, initialize RTCOR,
RTMCSR, and RFSHCR in that order, clearing bit PSRAME to 0 and setting bit DRAME to 1.
Set bit P8
1
DDR to 1 in the port 8 data direction register (P8DDR) to enable CS
3
output. In
ABWCR, make area 3 a 16-bit-access area.
Pseudo-Static RAM Interface: To set up area 3 for connection to pseudo-static RAM, initialize
RTCOR, RTMCSR, and RFSHCR in that order, setting bit PSRAME to 1 and clearing bit
DRAME to 0. Set bit P8
1
DDR to 1 in P8DDR to enable CS
3
output.
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