AN2798 Freescale Semiconductor / Motorola, AN2798 Datasheet - Page 7

• Manufacturer Part Number: AN2798
• Description: Migrating from the MPC855T to the MPC885
• Manufacturer: Freescale Semiconductor / Motorola

6 New Features for MPC885
The following sections discuss the new features of the MPC885.
6.1 Hardware Changes
The following are the hardware changes from the MPC885T to the MPC885:
Freescale Semiconductor
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Reserved space (offset 0xA20-0xA77) in the MPC855T is now for SCC2 and SCC3 in the MPC885.
Port E registers in the MPC885 reside in a previously reserved area of the Port B registers in the MPC855T
(starting at offset 0xAC8).
The registers mapped for the FEC registers in the MPC855T are now mapped for FEC1 for the MPC885.
The immediate reserved space following the FEC registers in the MPC855T is the location for the FEC2
registers in the MPC885 (starting at offset 0x1E00). For ease of porting, FEC2 registers are located in the
same order as FEC1, with offset for FEC2 equal to FEC1 plus 0x1000.
Dual-port RAM for both processors is from IMMR + 0x2000-0x2FFF, with expanded dual-port RAM from
0x3000-0x3BFF.
The MPC855T’s memory resources are mapped to a contiguous 64 Kbyte block; the MPC885’s memory
resources are mapped to a contiguous 256 Kbyte block, as shown in
block in the upper 128 Kbytes.
Bits 14–15 in the 16-bit field IMMR[ISB] have new meaning in the MPC885. When IMMR[ISB] bits 14–15
are cleared, the internal memory map is the same as in the MPC855T. When IMMR[14–15] = 10, an
additional 128 Kbyte memory block becomes available for the security engine, as shown in
DP[0-3]/IRQ[3:6] pins were removed.
No data parity generation /checking.
IRQ 3,4,6 exist in different pins. IRQ5 has no alternative pin.
The MPC885 only supports normal high and normal low power modes.
Location of contiguous 256-Kbyte block of internal memory resources in this figure is for illustration only.
The addresses shown are offsets from the IMMR.
1 Gbyte
2 Gbyte
3 Gbyte
4 Gbyte
0
Global Memory
Migrating from the MPC855T to the MPC885, Rev. 0
Figure 5. MPC885 Memory Map
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0x0_0000
0x1_0000
0x2_0000
0x3_0000
0x4_0000
128 Kbytes
Resources
64 Kbytes
Memory
Security
Block
Figure
5, that includes the security
New Features for MPC885
Figure
5.
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