
114
EPSON
S1C88848 TECHNICAL MANUAL
5 PERIPHERAL CIRCUITS AND THEIR OPERATION (Remote Controller)
5.13.4 Soft-timer mode
In the soft-timer mode, software controls the ON/
OFF time and timing of the carrier output. This
mode does not use the
τ (reference cycle)
generation circuit, REMOUT time generator and
interrupt control circuit that are used in the hard-
timer mode, and operates with the configuration as
shown in Figure 5.13.4.1.
OSC3
oscillation
circuit
fOSC3
RCDIV
REMC
REMSO
REM
(R26)
Carrier
generation
circuit
RCDUTY3–RCDUTY0
Fig. 5.13.4.1 REM circuit configuration in soft-timer mode
The ON/OFF control of the carrier output is done
using the REM forced output ON/OFF register
REMSO. By writing "1" to REMSO, the carrier is
output to the REM (R26) terminal and when "0" is
written, the REM (R26) terminal goes low level
(VSS). However, the carrier must be generated by
writing "1" to REMC before writing "1" to REMSO.
Figure 5.13.4.2 shows the timing chart in the soft-
timer mode.
REMC
Carrier
REMSO
REM (R26)
output
Fig. 5.13.4.2 Timing chart (soft-timer mode)
The remote output using REMSO is started in
synchronization with the carrier generation circuit
by the hardware.
REMSO
REM (R26)
output
Synchronized
Fig. 5.13.4.3 Carrier output control using REMSO
Note: Be sure to control the carrier output using
REMSO. Do not control the carrier output
using REMC by setting the REMSO register
to "1".
5.13.5 Hard-timer mode and REM interrupt
In the soft-timer mode, the CPU is occupied for the
remote output processing so that it has no
flexibility for execution of other routines. To
alleviate this problem, the S1C88848 supports the
hard-timer mode explained below.
In the hard-timer mode, the carrier ON/OFF, that is
controlled using the REM forced output ON/OFF
register REMSO in the soft-timer mode, is done in
the hardware by using the
τ (reference cycle)
generation circuit and the REMOUT time generator.
τ (reference cycle) is generated from the carrier by
dividing, and is used for reference of the carrier
ON/OFF time in the hard-timer mode. The
dividing ratio of
τ (reference cycle) is selected from
4 types by the software. The carrier ON/OFF time
can be set for each transmission data bit by the
software using
τ (reference cycle) as reference.
Furthermore, the interrupt function is provided so
that the setting can be done without synchronizing
with the timing of the carrier output.
The interrupt timing can also be set by the software
using
τ (reference cycle) as the reference same as
the ON/OFF time.
The circuit in the hard-timer mode is configured as
shown in Figure 5.13.1.2, and all the REM circuit is
used. However, REMSO that is used to control the
carrier output in the soft-timer mode should be
fixed at "0". If "1" is written to REMSO, REM output
are forcibly done regardless of the control of the
hard-timer mode.
■
τ (reference cycle)
τ (reference cycle) is used as reference for the
carrier output ON time and interrupt timing
specified by the software, and is generated by the
τ
(reference cycle) generation circuit by dividing
carrier. This dividing ratio can be selected using the
REM
τ cycle setting registers RT1 and RT0 from 4
types as shown in Table 5.13.5.1.
Table 5.13.5.1
τ (reference cycle) setting
fcarrier / 32
fcarrier / 20
fcarrier / 16
fcarrier / 12
RT1
1
0
RT0
1
0
1
0
τ dividing ratio
fcarrier indicates carrier frequency. It is selected
with the REM carrier cycle setting register
RCDIV.