EM6517 ETC, EM6517 Datasheet - Page 17

• Manufacturer Part Number: EM6517
• Description: 4 BIT MICROCONTROLLER
• Manufacturer: ETC

7.4 Port B
The EM6517-1 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.
7.4.1 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 13 for details.
7.4.2 Pull-up or Pull-down
Figure 13. Port B Architecture
On each terminal of PB[3:0] an internal input pull-up (metal mask MPBPU[n]) or pull-down (metal mask
MPBPD[n]) resistor can be connected per metal mask option. Per default the two resistors are in place. In this
case one can chose per software to have either a pull-up, a pull-down or no resistor. See below.
Internal Data Bus
Ck[16], Ck[12]
PWM, Ck[11],
Outputs are:
DB[n]
Multiplexed
Port B Direction Register
Port B Data Register
PBData[n]
PBIOCntl[n]
FOR ENGINEERING ONLY
Read
Output Active
Multiplexed
Multiplexed
Output
Read for PB[3:0]
Read
MUX
Option Register
NoPdPB[n]
Pull-down
Control
Port B
I / O Terminal
PB[n]
4
© EM Microelectronic-Marin SA, 09/99, Rev. A/277
Open Drain Option
NchOpDPB[n]
Register
Active
Pull-down
Mask Option
MPBPD[n]
mask option
MPBPD[n]
EM6517
Active Pull-up
in Nch. Open
Drain Mode
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