MOTOROLA
Chapter 1. Overview
1-5
When more than one 60x processor is used, nine signals of the L2 interface change their
functions (to BR[1–3], BG[1–3], and DBG[1–3]) to allow for arbitration between the 60x
processors. The 60x processors share all 60x interface signals of the MPC106, except the
bus request, bus grant, and data bus grant signals.
When an external L2 controller (or integrated L2 cache module) is used, three signals of the
L2 interface change their functions (to BRL2, BGL2, and DBGL2) to allow the MPC106
to arbitrate between the external cache and the 60x processor(s).
1.2.3 Memory Interface
The memory interface controls processor and PCI interactions to main memory and is
capable of supporting a variety of DRAM, extended data-out (EDO) DRAM, or
synchronous DRAM (SDRAM) and ROM or Flash ROM configurations as main memory.
The maximum supported memory size is 1 Gbyte of DRAM/EDO/SDRAM, with 16
Mbytes of ROM/Flash. The MPC106 configures its memory controller to support the
various memory sizes through software initialization of on-chip configuration registers.
Parity (DRAM/EDO/SDRAM) or ECC (DRAM/EDO-only) is provided for error
detection.
The MPC106 controls the 64-bit data path to main memory (72 bits with parity or ECC).
To reduce loading on the data bus, system designers may need to add buffers between the
60x bus and memory. The MPC106 features configurable data/parity buffer control logic to
accommodate several buffer types.
The MPC106 supports a variety of DRAM/EDO/SDRAM configurations. DRAM/EDO/
SDRAM banks can be built using dual in-line memory modules (DIMMs), single in-line
memory modules (SIMMs), or directly-attached memory devices. Thirteen multiplexed
address signals provide for device densities up to 16 M. Eight row address strobe/command
select (RAS/CS[0–7]) signals support up to eight banks of memory. The MPC106 supports
bank sizes from 2 Mbytes to 128 Mbytes. Eight column address strobe/data qualifier (CAS/
DQM[0–7]) signals are used to provide byte selection for memory bank accesses.
The MPC106 supports parity checking and generation in two forms—normal parity and
read-modify-write (RMW) parity. As an alternative to simple parity, the MPC106 supports
error checking and correction (ECC) for DRAM/EDO configurations. Using ECC, the
MPC106 detects and corrects all single-bit errors and detects all double-bit errors and all
errors within a nibble.
For ROM/Flash support, the MPC106 provides 20 address bits (21 address bits for the 8-bit
wide ROM interface), two bank selects, one output enable, and one Flash write enable. The
16-Mbyte system ROM space is subdivided into two 8-Mbyte banks. Bank 0 (selected by
RCS0) is addressed from 0xFF80_0000 to 0xFFFF_FFFF. Bank 1 (selected by RCS1) is
addressed from 0xFF00_0000 to 0xFF7F_FFFF. A configuration signal (FOE) sampled at
reset, determines the bus width of the ROM or Flash device (8-bit or 64-bit) in bank 0. The
data bus width for ROM bank 1 is always 64 bits. For systems using the 8-bit interface to