Calendar And Clock Generator; Keyboard Interface Lines - NEC Advanced Personal Computer System Reference Manual

Processor PCB
2-42
Table 2-11 Keyboard Interface Lines
PIN SIGNAL
1 Not used
2 Not used
3 Keyboard Data 1
4
Keyboard Data 2
5 Keyboard Data 3
6 Keyboard Data 4
7
Keyboard Data 5
8 Keyboard Data 6
9 Keyboard Data 7
10 Keyboard Data 8
11
Signal Ground
12 Data Strobe
13
Signal Ground
14
Not used
15 Not used
16 SWItch Strobe
17 Not used
18 Not used
19 Debug
20 Signal Ground
21
Signal Ground
22 Signal Ground
23
+5 Vdc
24 +5 Vdc
25 Not used
26 Not used
2.9 CALENDAR AND CLOCK GENERATOR
The Calendar and Clock Generator is supported by a CMOS Integrated Circuit
(IC) (NEC JlPDI990AC). This IC independently registers the month, day of the
month, day of the week, hour, minute, and second, and it can receive or send this
information from or to the microprocessor. Because this IC carries out all clock
functions, it frees the microprocessor from these duties, increasing the capabilities
of the microprocessor in other areas.