Datasheet

Chapter 3 Memory Mapping Control (S12XMMCV4)
MC9S12XE-Family Reference Manual Rev. 1.25
214 Freescale Semiconductor
3.4.2.5 Memory Configuration
Two bits in the MMCCTL1 register (ROMHM, RAMHM) configure the mapping of the local address
(0x4000-0x7FFF) in the global memory map.
ROMHM, RAMHM are write once in normal and emulation modes and anytime in special modes.
Three areas are identified (See Figure 3-21):
• Program FLASH (0x7F_4000-0x7F_7FFF) when ROMHM = 0.
• External Space (0x14_4000-0x14_7FFF) when ROMHM = 1 and RAMHM = 0.
• XSRAM Space (0x0F_C000-0x0F_FFFF) when ROMHM = 1 and RAMHM = 1.
Table 3-19 shows the translation from the local memory map to the global memory map taking in
consideration the different configurations of ROMHM and RAMHM.
Table 3-20 describes the application note of the RAM configuration and its dedicated global address.
Table 3-19. ROMHM and RAMHM Address Location
Local Address ROMHM RAMHM Global Address Location
0x4000 - 0x7FFF
0 X 0x7F_4000 - 0x7F_7FFF Internal Flash
1 0 0x14_4000 - 0x14_7FFF External Space
11
0x0F_C000 - 0x0F_FFFF Bottom of the Implemented RAM
0x2000 - 0x3FFF 0x0F_A000 - 0x0F_BFFF Fixed up to 8K RAM
0x2000 - 0x3FFF 1 0 0x0F_E000 - 0x0F_FFFF Fixed up to 8K RAM
Table 3-20. RAM Configuration
phase RPAGE ROMHM RAMHM RAM AREA Global Address
After reset RPAGE = 0xFD
(Reset value)
0 0 12 Kilobytes 0x0F_D000 - 0x0F_FFFF
During setup RPAGE = 0xFD
(Reset value)
1 1 24 Kilobytes 0x0F_A000 - 0x0F_FFFF
Normal Operation
(0x00 <= RPAGE <= 0xF9) 1 1 28 Kilobytes 0x00_0000 - 0x0F_9FFF
(0xFA <= RPAGE <= 0xFF) 1 1 24 Kilobytes 0x0F_A000 - 0x0F_FFFF