Kenwood PS-50, SP-430, PS-430, MB-430, AT-440, VS-1, YK-88C Fig Digital circuit, Key scan matrix

TS-440S

CIRCUIT DESCRIPTIO N

2. Digital display

FIP digit and segment signals are driven by the 6300 bu t decimal point and red character signals are driven by a tran - sistor . 8 V is used to increase the brightness of red charac - ters . The 7800 sends display data serially at 1 MHz, but th e clock signals are divided by two (500 kHz) in the 4080 an d fed into the 6300 . Figure 16 shows how the frequency divi - sion is accomplished . The 7800 sends data from its SO pi n

(pin 28) and a clock signal from its SCK pin (pin 26) at ap- prox . 1 ms intervals . After the 7800 has sent 8 bits of dat a five times, the 7800 sends a negative enable pulse from port B5 (pin 46) . When a decimal digit goes on, the 7800 set s port C4 to L and when a red character goes on the 780 0 sets port C3 to H .

Switch uni t

+5v

1~) N_ O Q, O I() e M N - 0 0 O 9 0 0 0 O U O O O 0

+g~

00 0 1 02 03 04 05 06 On 08 09 010 011 012 01 3 014 015 01 On 01 01 9 1 0 0 0 0 0 0 0 0 00 0 o c

------------------- -

L

20 bit Display buffer resisto r

IC3 TC40I3BP A/2

		C K		i	f'
28 O	9 D	0 13	S I		20bit Serial shift resisto r		s o
	CL P R			1 1 1-		---	fl->J
	10	8
p PD
7800G			c	contro l		IC I
				circuit
5			LH			pPD6300C
46
	IC3		s
	TC40I3BP B/ 2

26

D

SCK32

CL PR

Fig . 16 Digital circuit

3 . Key scan inpu t

The key scan input block sends key scan signals (negativ e pulses) from its 8255 (IC53) port C in the order of CO to C 7 (C6 and C7 are output only once when the POWER switc h is turned on) . When a matrix crossing point switch is on, its

corresponding bit in the 8255 port A is L to enable the switc h to be identified . Figure 13 shows the matrix . Key scan S 6 and S7 are provided for the extended function using diodes .

Key scan matrix			1		2		3	S	4			5		6
	1	1	LSB	2	USB	3	CW	4	AM		5		FM
	2	6		7		8		9			0	FSK
	3		V/M		MV		SCAN		M .IN			CLEAR		EN T
	4				RIT		ZIT	T-FSET				1MHz		DOW N
K	5				A/B		SPRIT		A=B		25L		1	U . P
	6		VOICE	T.SET ON			CLOCK 1	100L		3	50L		2	100U	8
	7	T .SET OFF						200L		4	25U		6	200U	9
	8		TIMER		SET		CLOCK 2	400L		5	501		7	400U	10

Table 10 . Key scan matrix

20