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MPC555
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MPC556
MODULAR INPUT/OUTPUT SUBSYSTEM (MIOS1)
MOTOROLA
USER’S MANUAL
Rev. 15 October 2000
15-6
15.5 MIOS1 Bus System
The internal bus system within the MIOS1 is called the modular I/O bus (MIOB). The
MIOB makes communications possible between any submodule and the IMB3 bus
master through the MBISM.
The MIOB is divided into three dedicated buses:
• The read/write and control bus
• The request bus
• The counter bus set
15.5.1 Read/Write and Control Bus
The read/write and control bus (RWCB) allows read and write data transfers to and
from any I/O submodule through the MBISM. It includes signals for data and address-
es as well as control signals. The control signals allow 16-bit simple synchronous sin-
gle master accesses and supports fast or slow master accesses.
15.5.2 Request Bus
The request bus (RQB) provides interrupt request signals along with I/O submodule
identification and priority information to the MBISM.
Note that some submodules do not generate interrupts and are therefore independent
of the RQB.
15.5.3 Counter Bus Set
The 16-bit counter bus set (CBS) is a set of two 16-bit counter buses. The CBS makes
it possible to transfer information between submodules. Typically, counter submod-
ules drive the CBS, while action submodules process the data on these buses. Note,
however, that some submodules are self-contained and therefore independent of the
counter bus set.
15.6 MIOS1 Programmer’s Model
The address space of the MIOS1 consist of four Kbytes starting at the base address
of the module. The MIOS1 base address is a multiple of the addressable range. The
overall address map organization is shown in
To find the base address of a given implementation, refer to
. To find the submodule base address, refer to
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Freescale Semiconductor, Inc.
For More Information On This Product,
Go to: www.freescale.com
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