Controlling Protocol ......
Interrupt Requests
An Interrupt (IRQ), when enabled, is provided by the FX803 to indicate the following conditions to the µController.
NOTONE Timer Period
Expired
G/Purpose Timer
Period Expired
Rx Tone Measurement
Complete
Enabled: By Control Register Bit 5.
Enabled: By Control Register Bit 6.
Enabled: By Control Register Bit 5.
Set: When the preset Notone Flag is
set.
Set: When the General Purpose Timer
has timed out.
Set: When an Rx Frequency
Measurement has been successfully
completed.
Identified: By Status Register Bit 1.
Identified: By Status Register Bit 2.
Identified: By Status Register Bit 0.
Cleared: By reading the Status
Cleared: By reading the Status
Register.
Cleared: By reading the Status
Register.
Register.
On recognition of the “Read Status” Command byte, the interrupt output is cleared, the Status Bits are transferred to the
µController via the “C-BUS” Reply Data line and the internal Status Bits are cleared.
Operational Recommendations
It is recommended that, following initial System power-up a General Reset command is sent to the FX803.
Receive Sequence
Transmit Control Sequence
1. Set Tone Frequency Generators to VBIAS (setting
both tone generators (Bit 13 = “1”)) during the
transmitter initialization period.
1. Send Control Command for Rx:
Select Midband/Highband and Digital Filter length.
2. Disable transmitters, if desired by writing to Tone
2. Send Control Command for Tx:
Select Sum/Switched Sum o/p and Audio Switch
states.
Frequency registers.
3. Prime the NOTONE Timer by sending the required
3. Send General Purpose (GP) Timer information for the
period byte.
VBIAS (NOTONE) transmitter initialization period (Step 1).
4. Enable Decoder interrupts as desired.
This will initiate the timer.
4. Enable the General Purpose Timer interrupt.
5. When a valid tone has been detected by a
successfully completed measurement the Status
Register is set to “Tone Measurement Complete” and
an interrupt sent to the µC.
5. µC waits for “GP Timer Expired;” Reads the Status
Register to check interrupt due to timer; Resets the
Status Bit.
If required, the µC sends the next timer period followed
by the next tone(s) frequency information.
A new timer period sent will reset the timer, otherwise
the timer is self-sequencing.
6. The µC examines the Status Register, if tone
measurement is complete, reads in the Rx Tone
Frequency in the form N + R (Figure 6).
6. The µC monitors the interrupts and repeats 5 & 6 as
7. Rx Tone Measurement Complete interrupts are
periodically sent to the µC unless NOTONE is detected,
in which case a NOTONE Interrupt is sent.
required.
7. After last loaded tone the µC turns off the Tone
Generator(s) by setting tone outputs to VBIAS (NOTONE)
(Tables 4 and 5).
Glossary of Abbreviations
General Reset
Below is a list of abbreviations used within this Data
Sheet.
Upon Power-Up the “bits” in the FX803 registers will be
random (either “0” or “1”). A General Reset Command
(01H) will be required to “reset” all microcircuits on the
“C-BUS,” and has the following effect upon the FX803.
fXTAL
Xtal/clock frequency
Audio input signal
Control Reg.
Set as 00H
Set as 00H
Set as 00H
Set as 0000H
Set as 0000H
Set as 00H
SINPUT
Status Reg. Bits 0, 1, 2.)
NOTONE Timer Reg.
fTONE
Tone frequency
Tone Gen. 1 Reg. (2 bytes)
Tone Gen. 2 Reg. (2 bytes)
Gen/Purpose Reg.
Sets the FX803 to:
Encoder High Band (625Hz to 3000Hz) – with interrupts
disabled, both timers set to 00H.
It is recommended that both timers are set-up before
interrupts are enabled, to prevent initial, undesired interrupts.
12
CMLMICRO [ CML MICROCIRCUITS ]
