ST72F264G ST Microelectronics, ST72F264G Datasheet - Page 43

• Manufacturer Part Number: ST72F264G
• Description: (ST72F260G - ST72F264G) 8-BIT MCU
• Manufacturer: ST Microelectronics

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DataSheet
I/O PORTS (Cont’d)
9.8 I/O PORT REGISTER DESCRIPTION
DATA REGISTER (DR)
Port x Data Register
PxDR with x = A, B or C.
Read /Write
Reset Value: 0000 0000 (00h)
Bits 7:0 = D[7:0] Data register 8 bits.
The DR register has a specific behaviour accord-
ing to the selected input/output configuration. Writ-
ing the DR register is always taken into account
even if the pin is configured as an input; this allows
always having the expected level on the pin when
toggling to output mode. Reading the DR register
returns either the DR register latch content (pin
configured as output) or the digital value applied to
the I/O pin (pin configured as input).
DATA DIRECTION REGISTER (DDR)
Port x Data Direction Register
PxDDR with x = A, B or C.
Read /Write
Reset Value: 0000 0000 (00h)
DD7
D7
7
7
4
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DD6
D6
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DD5
D5
DD4
D4
DD3
D3
DD2
D2
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DD1
D1
DD0
D0
0
0
Bits 7:0 = DD[7:0] Data direction register 8 bits.
The DDR register gives the input/output direction
configuration of the pins. Each bit is set and
cleared by software.
0: Input mode
1: Output mode
OPTION REGISTER (OR)
Port x Option Register
PxOR with x = A, B or C.
Read /Write
Reset Value: 0000 0000 (00h)
Bits 7:0 = O[7:0] Option register 8 bits.
For specific I/O pins, this register is not implement-
ed. In this case the DDR register is enough to se-
lect the I/O pin configuration.
The OR register allows to distinguish: in input
mode if the pull-up with interrupt capability or the
basic pull-up configuration is selected, in output
mode if the push-pull or open drain configuration is
selected.
Each bit is set and cleared by software.
Input mode:
0: Floating input
1: Pull-up input with or without interrupt
Output mode:
0: Output open drain (with P-Buffer unactivated)
1: Output push-pull (when available)
O7
7
O6
ST72260G, ST72262G, ST72264G
O5
O4
O3
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O2
O1
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O0
0
4U
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