S1C63666 TECHNICAL MANUAL
EPSON
43
CHAPTER 4: PERIPHERAL CIRCUITS AND OPERATION (Output Ports)
4.6.3 High impedance control
The output ports can be set into a high impedance status. This control is done using the high impedance
control registers.
The high impedance control registers are provided to correspond with the output ports as shown below.
High impedance control register
Corresponding output port
R00HIZ
R00 (1 bit)
R01HIZ
R01 (1 bit)
R02HIZ
R02 (1 bit)
R03HIZ
R03 (1 bit)
R1HIZ
R10–R13 (4 bits)
When "1" is written to the high impedance control register, the corresponding output port terminal goes
into high impedance status. When "0" is written, the port outputs a signal according to the data register.
4.6.4 Special output
In addition to the regular DC output, special output can be selected for the output ports R02 and R03 as
shown in Table 4.6.4.1 with the software.
Figure 4.6.4.1 shows the configuration of the R02 and R03 output ports.
Table 4.6.4.1 Special output
Terminal
R03
R02
Special output
FOUT
TOUT
Output control register
FOUTE
PTOUT
Data bus
Register
PTOUT
Register
R02
TOUT
R02
(TOUT)
Register
FOUTE
Register
R03
Register
R03HIZ
Register
R02HIZ
FOUT
R03
(FOUT)
Fig. 4.6.4.1 Configuration of R02 and R03 output ports
At initial reset, the output port data register is set to "0" and the high impedance control register is set to
"0". Consequently, the output terminal goes low (V
SS
).
When using the output port (R02, R03) as the special output port, fix the data register (R02, R03) at "1"
and the high impedance control register (R02HIZ, R03HIZ) at "0" (data output). The respective signal
should be turned on and off using the special output control register.
Note: • Be aware that the output terminal is fixed at a low (V
SS
) level the same as the DC output if "0" is
written to the R02 and R03 registers when the special output has been selected.
• Be aware that the output terminal shifts into high impedance status when "1" is written to the
high impedance control register (R02HIZ, R03HIZ).