Kontron PCI-AOB16/12, Руководство пользователя

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Programming the Digital I/O Circuit 5-9 PCI-AOB8/12 (16/12) User’s Guide
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The 8-bit control register is used to set the mode and direction of the ports.
Table 5-4. Control Register Bit Assignments
The circuit is initialized by the computer Reset command (all ports set for input and all buffers
enabled). Both the 8255 control register and the buffer direction latch are accessed at the same
address.
The 8255 control register will latch a new configuration byte when it's written to with bit D7
high. If, for example, hex 80 is sent to Base 23, the group 0 PPI will be configured in
mode 0 with ports A, B, and C as outputs.
Bit Assignment Function
D0 Port C Lo (C0-C3) 1 = Input, 0 = Output
D1 Port B 1 = Input, 0 = Output
D2 Mode Selection 1 = Mode 1, 0 = Mode 0
D3 Port C Hi (C4-C7) 1 = Input, 0 = Output
D4 Port A 1 = Input, 0 = Output
D5,D6 Mode Selection 01 = Mode 1, 00 = Mode 0 1X = Mode 2
D7 Mode Set Flag & Tristate 1 = Active & Tristate
Important: PPI Mode 1 cannot be used with this circuit without modification.
Thus, bits D2, D5, and D6 should always be set to "0". If your card has been
modified to operate in Mode 1, then there is an Addendum sheet in the front of this
manual describing that modification. This circuit cannot be modified to operate in
PPI Mode.