UPD784026 Renesas Electronics Corporation., UPD784026 Datasheet - Page 639

• Manufacturer Part Number: UPD784026
• Description: 16/8-bit Single-chip Microcontrollers
• Manufacturer: Renesas Electronics Corporation.

21.3.1 Control Registers
(1) Refresh mode register (RFM)
Remark
Caution The refresh function cannot be used when the bus hold function is used. In this case, ensure that
The RFM is an 8-bit register that controls the pseudo-static RAM refresh cycle and switching to self-refresh operations.
The RFM register can be read or written to with an 8-bit manipulation instruction or bit manipulation instruction. RFM
format is shown in Figure 21-15.
RESET input clears the RFM register to 00H and sets the REFRQ pin to port mode, so that it operates as the dual-
function P67 pin.
RFM
RFLV
refreshing is specified as disabled.
7
: 0 or 1
6
0
5
0
Figure 21-15 Refresh Mode Register (RFM) Format
CHAPTER 21 LOCAL BUS INTERFACE FUNCTION
RFEN
4
3
0
2
0
RFT1
1
RFT0
0
RFT1 RFT0
RFLV RFEN REFRQ Pin Output Control
* f
* f
0
0
1
1
0
1
CLK
CLK
0FFCCH
: Internal system clock frequency
: Internal system clock frequency
Address
0
1
0
1
0
1
Refresh Pulse Output Cycle
Specification
Port mode
Self-refresh operation
(REFRQ low level)
Refresh pulse output enabled
32/f
64/f
128/f
256/f
On Reset
00H
CLK
CLK
CLK
CLK
* (2.6
(5.1
(10.2
(20.5
R/W
R/W
s)
s)
s)
s)
f
CLK
=12.5 MHz
599