Intel
®
81341 and 81342—Clocking and Reset
Intel
®
81341 and 81342 I/O Processors
Developer’s Manual
December 2007
990
Order Number: 315037-002US
19.1.1.3 Clocking Region 3 (Internal Bus)
Region 3 covers the 81341 and 81342 internal bus and obtains is input clock from
either
/-
or
P_CLKIN
defending on the setting of the
CLK_SRC_PCIE#
strap. Region 3 operates at a frequency up to 400 MHz. All units interface to or reside
in this region. The units which interface to this region include the Intel XScale
®
processors, the Memory Controller Unit, ATU and bridge to the AHB bus. Units which
wholly reside within region 3 include the Application DMA, XSI Bridge, SMBus interface,
and Peripheral Bus interface.
Region 3 contains an open-drain bi-directional clock (SMBCLK) used by the SMBus
interface. The SMBCLK operates at a maximum clock frequency of 100 KHz.
19.1.1.4 Clocking Region 4 (Peripheral Bus Interface)
Region 4 obtains its input clock from the clocking unit specified in region 3. This region
operates at a fixed 66 MHz and depending on the frequency of region 3 may be an
asynchronous boundary.
19.1.1.5 Clocking Region 5
Region 5 obtains its input clock from the clocking unit specified in region 3. This region
is used for low-speed peripheral units. Currently, this includes:
• I
2
C bus interface
• General-Purpose I/O unit
• UART serial bus interface
Region 5 contains an output clock (SCL) used for the I
2
C bus interface. The SCL clock
frequency is 100 KHz or 400 KHz. SCL is generated from the internal bus clock with its
frequency determined by the Fast Mode bit in the
. The
UART input clock is driven at 16.67 MHz, and divided within the unit for the serial
interface baud rate.
19.1.1.6 Clocking Region 7 (Intel XScale
®
Processor)
Region 7 obtains its input clock from either
/-
or
P_CLKIN
defending on the
setting of the
CLK_SRC_PCIE#
strap. This region is the Intel XScale
®
processor
(ARM* architecture compliant). It supports clock frequencies up to a maximum of 1200
MHz operation. The region 7 clock is an integer multiple of the Internal Bus clock
(region 3).
19.1.1.7 Clocking Region 8 (DDR SDRAM)
Region 8 provides six DDR SDRAM output clocks, and the clocking for the Memory
Controller Unit. The clocking unit contains three output clocks, called
M_CK[2:0]
, and
three complement clock outputs called
M_CK[2:0]#
. The
M_CK[2:0]
and
M_CK[2:0]#
outputs are used by the DDR SDRAM memory subsystem. It supports
clock frequencies up to a maximum of 533 MHz operation for DDR533 SDRAM
The MCU operates at 1/2 the DDR frequency. A 2x clock is also required to drive all the
request strobes.
MCU DDR 2x Clock
200
400
400
267
533
533