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Introduction
MOTOROLA
MC68322 USER’S MANUAL
1-5
Figure 1-2. Graphics Unit Data Flow Diagram
1.2.3 Bus Interface Unit
The dual bus architecture of the MC68322 allows the printing workload to be distributed
among processing units and executed in parallel. The bus interface unit (BIU) allows the
core and graphics unit, which reside on the MC68322 bus and graphics bus, to function
independently. This is done through an arbitration unit which accommodates core accesses
to DRAM residing on the graphics bus. However, to print pages correctly, the graphics unit
gets higher priority than the core for DRAM accesses. The core performs instruction and
PROM data fetches without any impact to graphics bus operations. The BIU contains a
single-word, writeback buffer that reduces peak bus traffic generated by multiple active
modules. The writeback buffer provides a no-wait state write profile to the core and delays
the write until the graphics unit stops using the graphics bus.
1.2.4 System Integration Module
The system integration module (SIM) provides the ROM, PROM, and peripheral
chip-selects. It contains eight chip-select banks that can be programmed to decode
addresses and supply internal DTACK termination. These eight chip-select banks are
individually programmable for an address range of 256K to 64M. They can be located
anywhere within the 256M memory map and can be either contiguous or disjointed, as
required by the operating environment. Also, each chip-select bank can be independently
size or disabled.
The chip-selects for each bank can be set up to provide a wide range of timing parameters,
such as setup, access, hold, and recovery times for both read and write bus cycles. The
MC68322’s SIM provides internal bus cycle auto-acknowledge and the asynchronous WAIT
signal allows external devices to insert additional wait states as needed. The SIM also
allows SRAM to be added to the MC68322 bus for system stack space, temporary data
storage, or as a buffer for peripheral data.
MC68322
EC000
CORE
GRAPHICS UNIT
PRINT ENGINE
DRAM
DISPLAY
LIST
BAND1
BAND0
PROM
DRAM
CONTROL
RISC GRAPHICS
PROCESSOR (RGP)
PRINT ENGINE VIDEO
CONTROLLER (PVC)
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Freescale Semiconductor, Inc.
For More Information On This Product,
Go to: www.freescale.com
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