NXP Semiconductors MC9S12G - Page 261

S12G Memory Map Controller (S12GMMCV1)
MC9S12G Family Reference Manual Rev.1.27
NXP Semiconductors 263
Read: Anytime.
Write: Only if a transition is allowed (see Figure 5-4).
The MODC bit of the MODE register is used to select the MCU’s operating mode.
Figure 5-4. Mode Transition Diagram when MCU is Unsecured
5.3.2.2 Direct Page Register (DIRECT)
Read: Anytime
Write: anytime in special SS, write-once in NS.
This register determines the position of the 256 Byte direct page within the memory map.It is valid for both
global and local mapping scheme.
Table 5-4. MODE Field Descriptions
Field Description
7
MODC
Mode Select Bit — This bit controls the current operating mode during RESET
high (inactive). The external
mode pin MODC determines the operating mode during RESET
low (active). The state of the pin is registered
into the respective register bit after the RESET signal goes inactive (see Figure 5-4).
Write restrictions exist to disallow transitions between certain modes. Figure 5-4 illustrates all allowed mode
changes. Attempting non authorized transitions will not change the MODE bit, but it will block further writes to
the register bit except in special modes.
Write accesses to the MODE register are blocked when the device is secured.
Address: 0x0011
76543210
R
DP15 DP14 DP13 DP12 DP11 DP10 DP9 DP8
W
Reset00000000
Figure 5-5. Direct Register (DIRECT)
Normal
Single-Chip
1
Special
Single-Chip
0
(SS)
RESET
(NS)
1
01