Instruction manual

AMPDIO DRIVERS
Page 69
 Two I/O groups (Group A — also known as Group 0 or Group I)
(Group B — also known as Group 1 or Group II)
 Both groups contain an 8 bit port and a 4 bit control/data port
 Both 8 bit data ports can be latched input or latched output
Mode 2 provides strobed bi-directional operation using port A as the bi-directional data bus. Port
C3 to C7 bits are used for interrupts and handshaking bus flow control similar to mode 1. NOTE:
Port B and port C0 to C2 bits may be defined as mode 0 or 1, input or output in conjunction with
port A in mode 2.
 An 8 bit latched bi-directional bus port and 5 bit control port
 Both input and outputs are latched
 An additional 8 bit input or output port with a 3 bit control port
Single Bit Set/Reset Feature
With bit 7 'Command Select' set to '0', any of the eight bits of port C can be set or reset using a
single output instruction. This feature reduces the software overhead in control based applications.
When port C is being used as status/control for port A or port B, these bits can be set or reset
using the Bit Set/Reset operation just as if they were data output ports.
BIT ASSIGNMENTS
Bit layouts of the PPI command word register is shown below.
Command Word for Mode Definition Format
0 1 2 3 4 5 6 7
1 = I/O Mode
Group B
Port C (Lower)
1 = Input
0 = Output
Port B
1 = Input
0 = Output
Mode Selection
0 = Mode 0
1 = Mode 1
Group A
Port C (Upper)
1 = Input
0 = Output
Port A
1 = Input
0 = Output
Mode Selection
00 = Mode 0
01 = Mode 1
1X = Mode 2