
6-42
MPC106 PCIB/MC User's Manual
MOTOROLA
6.4.1 Supported SDRAM Organizations
It is not necessary to use identical memory devices in each memory bank; individual
memory banks may be of differing size. Although the MPC106 multiplexes the row and
column address bits onto 12 memory address signals, individual SDRAM banks may be
implemented with memory devices requiring fewer than 24 address bits. Note that the
MPC106 only supports devices that conform to the 16M JEDEC standard. It does not
support the 4M JEDEC standard.
Table 6-10 summarizes some of the memory configurations supported by the MPC106.
By using a memory polling algorithm at power-on reset, system firmware configures the
MPC106 to correctly map the size of each bank in memory (the memory boundary
registers). The MPC106 uses its bank map to assert the appropriate CS
n
signal for memory
accesses according to the provided bank depths.
6.4.2 SDRAM Address Multiplexing
System software must configure the MPC106 at power-on reset to appropriately multiplex
the row and column address bits for each bank. All 16M SDRAM devices use 12 row bits,
so the appropriate row bit parameters in MCCR1 should be set to 0b11. Address
multiplexing will then occur according to the configuration settings, as shown in
Figure 6-5.
Figure 6-23. SDRAM Address Multiplexing
During the row address phase, SDBA0 contains A9 and SDMA[1–11] contain A[10–20].
During the column address phase, SDBA0 contains A5, SDMA[1–3] contain A[6–8], and
SDMA[4–11] contain A[21–28].
Table 6-10. Memory Device Configurations Supported
Number of
Devices in a
Bank
Device
Configuration
Row Bits x
Column Bits
Bank Size
Maximum
Memory (Using
All 8 Banks)
16
4M x 4
12 x 12
32 Mbytes
256 Mbytes
8
2M x 8, 9
12 x 12
16 Mbytes
128 Mbytes
4
1M x 16, 18
12 x 12
8 Mbytes
64 Mbytes
Row x Col = 12x12,11,10,9
SDMA[4–11]
Row address bits (1–12)
BA0, SDMA[1–3]
A14
A0A1A2A3A4A5A6A7A8A9A10A11A12A13
A15A16A17A18A19A20A21A22A23A24A25A26A27A28A29A30A31
Column address bits
Physical address