Fisher CA-890 - Page 6

EXPLANATION
OF
FUNCTION
(TMP4270N)
System Outline of TMP4270N
This program operates an audio full remote control system SUB
CPU.
The system configuration is as follows.
SUB1 | es TUNER
<“— | TMP4270N C’ Main Unit
aoe DECK
“—| 1MP4270N eae: leses| Main Unit
Main CPU
TMP47C400
ee anes CD PLAYER
TMP4270N Pees, Sa Main Unit
RECORD
<> Rae C) /)\\ PLAYER
[= |S Mainunit
Main Micro-processor Control...
Outputs serial data received from the main micro-processor to
the appropriate mode key.
Main Unit Key Control...
Transmits the main unit function key and Mute inputs to the
main micro-processor.
Transmission/Reception
The sub micro-processor carries out 8 bit serial data reception
and transmission with the main micro-processor. !t takes data
from the main micro-processor and emits a 100ms-wide pulse
to the corresponding port. When the tact switches installed
connected to each port are depressed, the corresponding data
are transmitted to the main micro-processor.
The following ports are used for data
transmission and reception.
DATA | CLOCK READY | REQUEST
| Assignment
Transmission from Main to Sub Micro-processors.
1. Main micro-processor emits a REQ signal, and waits
approximately 3ms for sub micro-processor to receive REQ
signal.
Sub micro-processor enters data standby mode when REQ
signal is active.
Data and clock signals are transmitted from the main
micro-processor. The Sub micro-processor matches the
clock signal and reads the data. :
Main micro-processor clears the REQ and moves on to the
next assignment.
Sub micro-processor checks data _ received after °
acknowledging the REQ CLEAR and emits 100ms-wide
pulses to the port corresponding to the data code.
If the data is invalid or incomplete, the sub micro- processor
moves on to the next assignment without doing anything.
Checks only signals received from the main micro-
processor during generation of the 100ms-wide pulses. In
the event that valid data is once again received during pulse
generation, the sub micro-processor shuts the pulse off for a
30ms period and emits 100ms-wide pulses corresponding
to the new data code. Reception check at this time also.
Transmission from Sub to Main Micro-processors.
(DECK, PLAYER, etc., switches depressed, or MUTE at low)
Sub micro-processor emits a REQ signal and waits 2ms for
the unit to enter the READY mode; if the unit does not enter
the READY mode within the designated time period, the sub
micro-processor clears the REQ and proceeds to the next
assignment.
When the Main micro-processor detects the REQ signai, it
emits a READY signal within 2ms and enters data standby
mode.
If after the sub micro-processor has detected a READY
signal it does not detect data within a certain period of time
(designated differently for each mode), it transmits data with
the clock signal off. After this, it transmits both data and
clock signals, waits for the READY signal to go off once data
transmission has been completed, and clears REQ.
If the main micro-processor picks up the data, a READY
signal is cleared.
Main micro-processor checks the data and switches the
corresponding function, transmitting a code to the sub
micro-processor if necesary.
1.