66
Bit 0—RAM Enable (RAME):
Enables or disables the on-chip RAM. The RAME bit is
initialized by a reset, but is not initialized in the software standby mode.
Bit 0: RAME
Description
0
The on-chip RAM is disabled.
1
The on-chip RAM is enabled.
(Initial value)
3.3
Mode Control Register (MDCR)
Bit
7
6
5
4
3
2
1
0
EXPE
*
1
—
—
—
—
—
MDS1
MDS0
Initial value
Read/Write
—
*
2
R/W
*
2
1
—
1
—
0
—
0
—
1
—
—
*
2
R
—
*
2
R
Notes:
*
1 H8/3337SF (S-mask model, single-power-supply on-chip flash memory version) only.
Otherwise, this is a reserved bit that is always read as 1.
*
2 Determined by the mode pins (MD
1
and MD
0
).
The mode control register (MDCR) is an 8-bit register that indicates the operating mode of the
chip.
Bit 7—Expanded Mode Enable (EXPE):
Functions only in the H8/3337SF (S-mask model,
single-power-supply on-chip flash memory version). For details, see section 21.1.6, Mode Control
Register (MDCR).
In models other than the H8/3337SF, this is a reserved bit that cannot be modified and is always
read as 1.
Bits 6 and 5—Reserved:
These bits cannot be modified and are always read as 1.
Bits 4 and 3—Reserved:
These bits cannot be modified and are always read as 0.
Bit 2—Reserved:
This bit cannot be modified and is always read as 1.
Bits 1 and 0—Mode Select 1 and 0 (MDS1 and MDS0):
These bits indicate the values of the
mode pins (MD
1
and MD
0
), thereby indicating the current operating mode of the chip. MDS1
corresponds to MD
1
and MDS0 to MD
0
. These bits can be read but not written. When the mode
control register is read, the levels at the mode pins (MD
1
and MD
0
) are latched in these bits.
3.4
Address Space Map in Each Operating Mode
Figures 3.1 to 3.3 show memory maps of the H8/3337Y, H8/3336Y, H8/3334Y, H8/3397,
H8/3396, and H8/3394 in modes 1, 2, and 3.