vsc055xkm-01 Maxim Integrated Products, Inc., vsc055xkm-01 Datasheet - Page 21

• Manufacturer Part Number: vsc055xkm-01
• Description: Enhanced I?c Backplane Controller
• Manufacturer: Maxim Integrated Products, Inc.

VSC055-01
Data Sheet
3.2
3.2.1
Control Register Definitions
The control register definitions provides a bit-level description of all register bits, including power on and
default values. The terms set and assert refer to bits that are programmed to a binary 1. The terms reset, de-
assert, and clear refer to bits that are programmed to a binary 0. Reserved bits are represented by RES and
always return an unknown value. These bits should be masked. Bits that are reserved should never be set to
a binary 1, because these bits may be defined in future versions of the device.
00h: General-Purpose I/O Port 0 Data (GPD0)
The following table shows the bit assignments for the General-Purpose I/O Port 0 Data register.
Register Name:
Address:
Reset Value:
Bit
7:0
Bit Label
GPD0.7–0
GPD Read Data
GPD Write Data
DD Read Data
DD Write Data
GPD0
00h
XXXX_XXXXb
Access Description
Figure 3. I/O Port Block Diagram
R/W
General-Purpose Data
When the I/O pin is enabled as an output, writing these bits determines the data value
that will be present on the corresponding I/O pin.
If the I/O pin is enabled as an input, reading these register bits represent the current
voltage applied to the pin. At no time do the bits directly represent the value latched
into the data register.
If a pin is enabled as an input and there is no signal applied, weak internal pull-up
resistors hold the pin at a binary 1.
After a reset or power on, the register bits are set to a binary 1, however, the value
returned from a register read is the level applied to the pin since each pin is an input
by default.
D
D
CK
CK
Filter
Q
Q
21 of 133
I/O Port
January 2008
Revision 4.1