
S1C88409 TECHNICAL MANUAL
EPSON
75
CHAPTER 5: PERIPHERAL CIRCUITS AND OPERATION (Output Ports)
5.7 Output Ports (R ports)
5.7.1 Configuration of output ports
The S1C88409 has 30 bits of output ports.
R0 port:
R00–R07
8 bits
R1 port:
R10–R17
8 bits
R2 port:
R20–R27
8 bits
R3 port:
R30–R32
3 bits
R4 port:
R40–R42
3 bits
Depending on the bus mode setting, the configura-
tion of the output ports may vary as shown in the
table below.
Table 5.7.1.1 Configuration of output ports
R00
R01
R02
R03
R04
R05
R06
R07
R10
R11
R12
R13
R14
R15
R16
R17
R20
R21
R22
R23
R24
R25
R26
R27
R30
R31
R32
R40
R41
R42
Output port R00
Output port R01
Output port R02
Output port R03
Output port R04
Output port R05
Output port R06
Output port R07
Output port R10
Output port R11
Output port R12
Output port R13
Output port R14
Output port R15
Output port R16
Output port R17
Output port R26
Output port R27
Single chip
Bus mode
Terminal
Expanded 64K
Expanded 4M
Address A0
Address A1
Address A2
Address A3
Address A4
Address A5
Address A6
Address A7
Address A8
Address A9
Address A10
Address A11
Address A12
Address A13
Address A14
Address A15
Output port R20
Output port R21
Output port R22
Output port R23
Output port R24
Output port R25
RD signal
WR signal
Output port R30/CE0 signal
Output port R31/CE1 signal
Output port R32/CE2 signal
Address A16
Address A17
Address A18
Address A19
Address A20
Address A21
Output port R30
Output port R31
Output port R32
Output port R40
Output port R41
Output port R42
This section explains only the control of general-
purpose output ports. Refer to Section 5.2, "System
Controller and Bus Control", for the bus control.
Figure 5.7.1.1 shows the structure of the output
port.
VDD
VSS
Rxx
Data
bus
Address
Data register
Address
High impedance
control register
Fig. 5.7.1.1 Structure of output port
The data register and high impedance control
register of the output port which is used for the
bus function can be used as general purpose
registers with the ability to read and write. They
do not affect the bus signal output.
5.7.2 High impedance control
Each output port can be set in high impedance by
software. Thus the output signal lines can be
shared with other external devices.
By setting the bits of the high impedance control
register to "1", the corresponding output ports go
to a high impedance status. The output port in
which the register is set to "0" becomes a comple-
mentary output.
5.7.3 DC output
As shown in Figure 5.7.1.1, when "1" is written to
the output port data register, the output terminal
goes high (VDD) level and when "0" is written it
goes low (VSS) level.
The data written to the data register during high
impedance status is output from the terminal
when the output is switched to complementary.
5.7.4 Special output
The R40 to R42 terminals are shared with the
special output terminals shown in Table 5.7.4.1.
Table 5.7.4.1 Special outputs
Output port
R40
R41
R42
Special output
Clock output : TOUT0/FOUT3
Clock output : TOUT1/FOUT1
Buzzer output : BZ
When using a special output, fix the high-imped-
ance control register HZR4x of the port to "0" and
the output data register R4xD to "1".
Refer to Section 5.9, "Clock Output", for the TOUT
and FOUT outputs, and to Section 5.15, "Sound
Generator", for the BZ output.