Kenwood SP-430, PS-50, PS-430, MB-430, AT-440, VS-1 1 9 L, Fig A/D convertor circui t, RIT If Shift

4. Static input

7800 (ICI)

CO	Encoder U/D signa l
C 2	Unlock signa l

074052 (IC : Display)

8255 (IC53 )

BO	Lock switc h
B2	AT switc h
B3	MIC UP switc h
B4	MIC DOWN switc h
B5	PTT switc h
B7	VS-1 busy signal

CIRCUIT DESCRIPTIO N

"H" when U P
"L" when unloc k
A/D convertor dat a	A K
	D O
"L" when switch o n
"L" when switch o n
"L" when switch o n
"L" when switch o n
"L" when switch o n
"H" when VS-1 busy

TS-440S

2 --%--- 1 9 L

A/D converter Inpu t

Fig . 17 A/D convertor circui t

Table 1 1 .

5 . A/D convertor inpu t

Voltages controlled by the RIT and IF shift VRs are applie d to the 4052 (IC2 : Display) . The 4052 has four analog inputs : AO (IC2 pin 4) is connected to the IF shift VR, and Al (pi n

5)is connected to the RIT VR, the other two inputs are not used . When reading IF shift data, the 7800 sets port C5 t o 0 and selects 4052 AO . As a result, the 3255 sends a posi - tive pulse from port BO to reset the 4052, and the 780 0 sends nine positive pulses from port C6, and port C7 receive s data . When reading RIT data, the 7800 sets CO from th e 4052 to H and thereafter performs the same operations as when reading IF shift data .

I) RIT 2) IF SHIFT

6 . AT control

When the AT switch is turned on with the AUTO/THR U switch in the AUTO position, 8255 (IC53) ports B2 and B 5 go on . When the 7800 knows that the AT switch is on vi a port B2, it will enter the CW-mode, and sets port A2 to H and A0, Al, and A3 to A6, and B4 to L, and transfer a pow- er down signal . The 7800 then knows that the PTT switc h is on via 8255 port B5, and sets port A6 (transmission con- trol signal) to H, enabling transmission . However, if the select - ed frequency does not allow the 7800 to prepare fo r transmission, 7800 port A6 remains L and the 7800 will not enable transmission . When the selected frequency is 1 .9 MH z or less, the 7800 will not enter CW mode nor send a powe r down signal .

7. LED outpu t

Depending on the mode, the 7800 makes the 8255 (IC2 ) send M, SCR, 1 MHz, and lock LED signals from ports B4 , B5, and B6 . When the LED goes on, these ports are L .

When the mode LED is on, 7800 ports AO to AS are H . AO to A5 correspond to LSB, USB, CW AM, FM, and FSK respec - tively . Mode LED output is used as mode control signals i n the IF unit .

8. VS-1 (option )

When the voice switch is turned on, an address correspond- ing to the instruction (numerical data) entered is sent fro m 8255 (IC2) ports AO to A4 and a positive start pulse signa l is sent from port A5 . The VS-1 sends busy signals (H) to 8255 (IC53) port B7 while the voice switch is on . After th e voice switch goes off, an address corresponding to the nex t instruction and a start signal are sent .

MB 4052

9. µPD 7800 reset circuit

I

The 7800 reset circuit is used to initialize the 7800 whe n the POWER switch is turned on . This circuit supplies a rese t pulse to the 7800 after the clock is supplied to the 7800 sys - tem clock input, X1 (pin 31) . Since IC3 remains on unti l PST520D (IC3) pin 1 reaches 4 .3 V, C10 is not charged, ena - bling a reset signal to be supplied . When pin 1 exceeds 4 . 3 V, IC3 goes off, causing C10 to charge via R2 and R3 an d the reset signal is removed .

2 1