em6521 EM Microelectronic, em6521 Datasheet - Page 18

• Manufacturer Part Number: em6521
• Description: Mfp Version Of Em6621 Ultra Low Power Microcontroller With 4x20 Lcd Driver
• Manufacturer: EM Microelectronic

6.4 Port B
The EM6521 has one four bit general purpose I/O port. Each bit can be configured individually by software for
input/output, pull-up, pull-down and CMOS or Nch. open drain output type. The port outputs either data,
frequency or PWM signals.
6.4.1 Input / Output Mode
Each port B terminal is bit-wise bi-directional. The input or output mode on each port B terminal is set by writing
the corresponding bit in the RegPBCntl control register. To set for input (default), 0 is written to the
corresponding bit of the RegPBCntl register which results in a high impedance state for the output driver. The
output mode is set by writing 1 in the control register, and consequently the output terminal follows the status of
the bits in the RegPBData register.
The port B terminal status can be read on address RegPBData even in output mode. Be aware that the data
read on port B is not necessary of the same value as the data stored on RegPBData register.
See also
Figure 11. Port B Architecture
Copyright © 2005, EM Microelectronic-Marin SA
Internal Data Bus
F igure 11 for details.
1 1 5 H
R
PWM, Ck[16],
Ck[11], Ck[1]
DB[n]
Outputs are:
Multiplexed
Port B Direction Register
Port B Data Register
DDR[n]
DR[n]
Read
Output Active
Multiplexed
Multiplexed
Output
Read for PB[3:0]
Read
MUX
18
Option Register
Pull-down
Control
Port B
Pd[n]
I / O Terminal
PB[n]
4
Open Drain Option
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Register
OD[n]
EM6521
Active
Pull-down
Mask Option
MPBPD[n]
mask option
MPBPD[n]
Active Pull-up
in Nch. Open
Drain Mode