Datasheet

Chapter 3 Memory Mapping Control (S12XMMCV4)
MC9S12XE-Family Reference Manual Rev. 1.25
Freescale Semiconductor 193
3.3.2 Register Descriptions
3.3.2.1 MMC Control Register (MMCCTL0)
Read: Anytime. In emulation modes read operations will return the data from the external bus. In all other
modes the data is read from this register.
Write: Anytime. In emulation modes write operations will also be directed to the external bus.
The MMCCTL0 register is used to control external bus functions, like:
• Availability of chip selects. (See Table 3-5 and Table 3-6)
• Control of different external stretch mechanism. For more detail refer to the S12X_EBI
BlockGuide.
CAUTION
XGATE write access to this register during an CPU access which makes use
of this register could lead to unexpected results.
Address: 0x000A PRR
76543210
R
CS3E1 CS3E0 CS2E1 CS2E0 CS1E1 CS1E0 CS0E1 CS0E0
W
Reset 0000000
ROMON
1
1. ROMON is bit[0] of the register MMCTL1 (see Figure 3-10)
= Unimplemented or Reserved
Figure 3-3. MMC Control Register (MMCCTL0)
Table 3-5. Chip Selects Function Activity
Register Bit
Chip Modes
NS SS NX ES EX ST
CS0E[1:0], CS1E[1:0],
CS2E[1:0], CS3E[1:0]
Disabled
(1)
1. Disabled: feature always inactive.
Disabled Enabled
(2)
2. Enabled: activity is controlled by the appropriate register bit value.
Disabled Enabled Disabled