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Intel
®
IXP45X and Intel
®
IXP46X Product Line of Network Processors—GPIO Controller
Intel
®
IXP45X and Intel
®
IXP46X Product Line of Network Processors
Developer’s Manual
August 2006
784
Reference Number: 306262-004US
15.5.7
GPIO Clock Register
This register controls the use of GPIO15 and GPIO14 as clock outputs. GPOER defines
the output enable for the driver; this register controls both the clock dividers and a
MUX between the clock data and the data defined in GPOUTR. This register defines two
four bit counts for a clock divider running from the pclk clock, one defines the period of
the clock and the other defines the duty cycle. After early reset has been deasserted,
GPIO 15 will be defined as a pclk/2 output clock (33 MHz assuming 66 MHz pclk), with
the expectation that this might be used to control the expansion bus peripherals. The
expansion bus requires an external clock to operate; it could be provided from GPIO15
or an external frequency source. As defined in GPOER, GPIO14 is an input at reset.
There are two special cases for these counters. First, if the TC is defined as ‘0’ then the
counter is disabled and the clock output will be high. Second, if both TC and DC are ‘F’,
then the output clock will be pclk/2. If DC is = TC, then the clock output will be high.
Register
GPIT2R
Bits
Name
Description
Reset
Value
Access
31:2
4
(Reserved)
Not used. Ignored on writes and driven logic ‘0’ on reads.
0x0
RO
23:2
1
GPIO15
Not used
0x0
RW
20:1
8
GPIO14
Not used
0x0
RW
17:1
5
GPIO13
Not used
0x0
RW
14:1
2
GPIO12
000 – Active High
001 – Active Low
010 – Rising Edge
011 – Falling Edge
1xx – Transitional
000
Active High
RW
11:9
GPIO11
As per GPIO12
000
Active High
RW
8:6
GPIO10
As per GPIO12
000
Active High
RW
5:3
GPIO9
As per GPIO12
000
Active High
RW
2:0
GPIO8
As per GPIO12
000
Active High
RW
Register Name:
GPCLKR
Physical Address:
0xC8004018
Reset Hex Value:
0x01100000
Register Description:
This register controls the use of GPIO 15 and GPIO14 as clock sources
Access: Read/Write
3
1
1
6
1
5
8
7
0
(Reserved)
Mx
1
5
CLK1TC
CLK1DC
Mx
1
4
CLK0TC
CLK0DC