96
11. SYSTEM REGISTERS
Three system registers are used to control and monitor a variety of functions on the
ZT 8904. These registers are implemented with the same Ziatech 16C50A ASIC that
implements the 24 parallel I/O lines discussed in "
Parallel I/O
," Chapter 10. The
16C50A operating instructions are outlined below. Refer to "Parallel I/O" for a complete
discussion.
•
The reset state for all bits is a logical 0.
•
Bits dedicated to input operation must remain programmed with a logical 0 to
prevent contention with the input device.
•
Bits dedicated to output operation have readback capabilities.
PROGRAMMABLE REGISTERS
The following illustrate the three System registers.
7
6
5
4
3
2
1
0
System Register 0
VID IDE
MOD
RS2 RS1 RS0
WDR
RSV
Reserved
Watchdog Timer
0 Reset Stage 1 Timeout
1 Enable Watchdog Operation
Battery-Backed RAM Page
000 Page 0
001 Page 1
010 Page 2
011 Page 3
100 Page 4
101 Page 5
110 Page 6
111 Page 7
Boot Flash
0 Module
1 Local
IDE Interrupt
0 Local
1 System
Video BIOS
0 Local
1 System
System Register 0