Keyboard/RPG Problems

Keyboard Interface

See function block G of A3 Interface Assembly Schematic Diagram (sheet 3 of 6).

A pressed key results in a low on a keyboard sense line (LKSNSO through LKSNS7). This sets the output of NAND gate U607 high, generating KBD/RPG-IRQ. The CPU determines the key pressed by setting only one keyboard scan line (LKSCNO through LKSCN5) low through U602 and reading the keyboard sense lines.

1.If none of the keys or RPG responds, check ribbon cable, AlAlWl. (This cable connects the AlAl Keyboard to the A3 Interface assembly.) The keys are arranged in a row/column matrix, as shown in Table 7-4.

2.If an entire row or column of keys does not respond, and the RPG does respond, there might be an open or shorted wire in AlAlWl.

Table 7-4. Keyboard Matrix

LKSNS2 LKSNS3 LKSNS4 LKSNS5 t LKSNSG 1 LKSNS7

LKSCNO

 

 

 

 

RECALL

GHz

MHz /

k~z ,,“z,,

/,,:,,,

LKSCNl

MODULE

 

 

TRIG

DISP

9

6

 

 

 

 

 

 

 

 

I

 

 

 

 

 

 

 

 

 

 

LKSCNZ

PEAK

 

 

BW

TRACE

8

5

 

2

 

0

1

 

 

SEARCH

 

 

 

 

 

 

 

I

I

 

 

LKSCNS

FREQ

 

 

AUTO

MKR-+

7

4

 

1

 

0

HOLD

 

COUNT

 

 

COUPLE

 

 

 

 

 

 

 

 

 

LKSCN4

SWEEP

 

 

SK1

SK2

SK3

SK4

SK5

 

SK6

MKR

LKSCNS

AUX

 

 

MEAS/USER

CAL

SGL

COPY

FRE-

 

S P A N

AMPLI-

 

 

 

 

 

 

SWP

 

 

QUENCY

 

 

TUDE

 

C T R L

1

 

 

 

 

 

 

3.Check that all inputs to NAND gate A3U607 (LKSNS lines) are high when no key is pressed. If any input is low, continue with the following:

a.Disconnect AlAlWl from A3J602 and again check all inputs to U607.

b.If any input is low with AlAlWl disconnected, suspect A3U604, A3U607, or A3U602.

c.Reconnect AlAlWl to A3J602.

4.Monitor A3U607 pin 8 with a logic probe. A TTL high should be present when any key is held down. Monitor this point while pressing each key in succession.

5.Check that the LKSCN lines (outputs of A3J602 pins 1 through 6) read a TTL low with no key pressed. (Any TTL high indicates a faulty A3 Interface assembly.)

6.Check that a pulse is present at each LKSCN output of U602 when a key is pressed.

7.Check that only one input to U607 (LKSNS lines) goes low when a key is pressed.

8.Check that U602 pin 9 (LKBD-RESET) pulses low when a key is pressed.

9.If LKBD-RESETis incorrect and a pulse is not present at each of the LKSCN outputs of U602 when a key is pressed, check for LWRCLK and LSCAN-KBD.

ADCpnterface Section 7-7