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<a name="1204669"> </a><font color="#003366" face="Verdana, Arial, Helvetica, sans-serif">15.3 Internal peripheral space</font>
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<a name="1204670"> </a><font size=2 face="Verdana, Arial, Helvetica, sans-serif">The interconnect used on ST20-C2 base systems has two distinct uses.</font>
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<p> <font size=2 face="Verdana, Arial, Helvetica, sans-serif"><li ><a name="1204671"> </a>Subsystems use the `channel protocol' which is uses the physical layer of the command bus. Subsystem channels are placed at addresses below <em>MemStart</em>.</font></p>
<p> <font size=2 face="Verdana, Arial, Helvetica, sans-serif"><li ><a name="1204672"> </a>Internal peripherals are memory mapped devices on the command bus. These peripherals should be mapped to addresses in <em>PeripheralSpace</em> (address range #20000000 to #3fffffff). They are accessed via the device memory access instructions (for example, <strong>devlw</strong>, <strong>devsw</strong>). When used with addresses in this range the device access instructions they perform a transaction across the command bus rather than the memory bus. </font></p>
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<a name="1204673"> </a><font size=2 face="Verdana, Arial, Helvetica, sans-serif">The current convention is that <em>PeripheralSpace</em> is allocated to peripherals in 4燢byte blocks. The first three such blocks are reserved for use by the interrupt, EMI and low-power controller peripherals.</font>
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<font size=1 face="Verdana, Arial, Helvetica, sans-serif"> © 1997, 2001, 2002, 2003 STMicroelectronics. All Rights Reserved.<br>
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