OM6272,598 NXP Semiconductors, OM6272,598 Datasheet - Page 7

• Manufacturer Part Number: OM6272,598
• Description: DEMO BOARD UART TO I2C
• Manufacturer: NXP Semiconductors

Specifications of OM6272,598

• Main Purpose: Interface, I2C Master to UART
• Embedded: No
• Utilized Ic / Part: SC18IM700
• Primary Attributes: UART to I2C Master/GPIO Bridge, 4-Bit LED Dimmer
• Secondary Attributes: Graphic User Interface
• Lead Free Status / RoHS Status: Not applicable / Not applicable
• Other names: 568-3512; 935282853598; OM6272

Philips Semiconductors
5. Using the 8-bit programmable GPIO port
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Application note
GPIO 0 to GPIO 7 ports may be configured by the host to one of four types. These are:
quasi-bidirectional, push-pull, open-drain, and input-only. Two bits are used to select the
desired configuration for each port pin. PortConf1 is used to select the configuration for
GPIO[3:0], and PortConf2 is used to select the configuration for GPIO[7:4]. Each port pin
has Schmitt triggered input that also has a glitch suppression circuit.
Table 3:
Normally to read the actual state of the input pins the host must read the IOState register,
or to write to any of the output pins the host would perform a write to the IOState register.
But, there are two commands that can be used to simplify the process of controlling the
GPIO port: they are the ‘I’ and the ‘O’ commands. Instead of reading and writing to the
IOState register, the host would send these two commands in form of a message.
Let’s say GPIO0 to GPIO3 are programmed as inputs, and GPIO4 to GPIO7 are
programmed as outputs, and the host wants to read the state of all of the input pins and to
set all the output pins to 1.
To read the input pins the host sends this message to SC18IM700:
The SC18IM700 will return a byte to the host through the UART port, bit 3 to bit 0 of this
byte indicate the actual state of the input pins; bit 7 to bit 4 indicate the actual state of the
output pins.
To set the output pins, the host sends this message to SC18IM700:
Where the ‘X’ can be any value and will not have any effect because GPIO3 to GPIO0 are
programmed as inputs. GPIO7 to GPIO4 should all go HIGH once this message is sent.
IOx.1
0
0
1
1
I P
O FX P
Port configurations
IOx.0
0
1
0
1
Rev. 01 — 5 December 2005
How to use the SC18IM700 to control any I
Port configuration
quasi-bidirectional output configuration
push-pull output configuration
input-only configuration
open-drain output configuration
© Koninklijke Philips Electronics N.V. 2005. All rights reserved.
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C-bus device
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