dsp56800eerm Freescale Semiconductor, Inc, dsp56800eerm Datasheet - Page 42

• Manufacturer Part Number: dsp56800eerm
• Description: 16-bit Digital Signal Controllers
• Manufacturer: Freescale Semiconductor, Inc

4.2 Program Map
The operating mode control bits (MA and MB) in the Operating Mode Register (OMR) control the
Program memory map. At reset, these bits are set as indicated in
map configurations that are possible at reset. After reset, the OMR MA bit can be changed and will have
an effect on the P-space memory map, as shown in
effect
The device’s external memory interface (EMI) can operate much like the 56F80x family’s EMI, or it can
be operated in a mode similar to that used on other products in the 56800E family. Initially, CS0 and CS1
are configured as PS and DS, in a mode compatible with earlier 56800 devices.
Eighteen address lines are required to shadow the first 192K of internal program space when booting
externally for development purposes. Therefore, the entire complement of on-chip memory cannot be
accessed using a 16-bit 56800-compatible address bus. To address this situation, the EMI_MODE pin can
be used to configure four GPIO pins as Address[19:16] upon reset (Software reconfiguration of the highest
address lines [A20-23] is required if the full address range is to be used.)
The EMI_MODE pin also affects the reset vector address, as provided in
be configured as address or chip select signals to access addresses at P:$10 0000 and above.
Note: Program RAM is NOT available on the 56F8157 device.
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1. This bit is only configured at reset. If the Flash secured state changes, this will not be reflected in MB until the next reset.
2. Changing MB in software will not affect Flash memory security.
Flash Secured
OMR MB =
OMR MA
State
0
1
0
0
1
1
1, 2
Table 4-3 Changing OMR MA Value During Normal Operation
Use internal P-space memory map configuration
Use external P-space memory map configuration – If MB = 0 at reset, changing this bit has no
effect.
EXTBOOT Pin
OMR MA =
0
1
0
1
Table 4-2 OMR MB/MA Value at Reset
Mode 0 – Internal Boot; EMI is configured to use 16 address lines; Flash
Memory is secured; external P-space is not allowed; the EOnCE is disabled
Not valid; cannot boot externally if the Flash is secured and will actually
configure to 00 state
Mode 0 – Internal Boot; EMI is configured to use 16 address lines
Mode 1 – External Boot; Flash Memory is not secured; EMI configuration is
determined by the state of the EMI_MODE pin
56F8357 Technical Data, Rev. 15
Chip Operating Mode
Table
Chip Operating Mode
4-3. Changing the OMR MB bit will have no
Table
4-2.
Table
Table 4-4
4-4. Additional pins must
Freescale Semiconductor
shows the memory
Preliminary