10. Parallel I/O
90
16C50A Enhanced Operating Mode
Enhanced operation adds extended event sense and input debounce capabilities. It is
selected with four consecutive writes of 07h, 0Dh, 06h, and 12h to I/O port address 7Dh
immediately after a power cycle or a reset. Three enhanced register banks are selected
by programming bits 6 and 7 of I/O port 7Fh with a 00 for bank 0, a 01 for bank 1, and a
10 for bank 2. Ziatech Industrial Computer Systems software configures the 16C50A for
enhanced operation. The Ziatech BIOS initializes the ZT 8904 for enhanced operation
at BIOS revision 4.41 or later.
Enhanced Bank 0 I/O Port Addressing
Address
Register
Read Operation
Write Operation
0078h
Port 0 Data
MOD00-MOD07
MOD00-MOD07
0079h
Port 1 Data
MOD08-MOD15
MOD08-MOD15
007Ah
Port 2 Data
MOD16-MOD23
MOD16-MOD23
007Bh
System Register 0
-----
-----
007Ch
System Register 1
-----
-----
007Dh
System Register 2
-----
-----
007Eh
Reserved
-----
-----
007Fh
Write Inhibit/Bank Address
Status
Control
Enhanced Bank 1 I/O Port Addressing
Address
Register
Read Operation
Write Operation
0078h
Port 0 Event Sense
Status
Control
0079h
Port 1 Event Sense
Status
Control
007Ah
Port 2 Event Sense
Status
Control
007Bh
Reserved
-----
-----
007Ch
Reserved
-----
-----
007Dh
Reserved
-----
-----
007Eh
Event Sense Manage
Status
Control
007Fh
Bank Address
Status
Control