Zilog Z08470 Manual de usuario descargar pdf (Pagina 203)

UM008101-0601 Parallel Input/Output

3. Bidirectional mode: When this signal is active, data from the Port A

output register is gated onto Port A bidirectional data bus. The

positive edge of the strobe acknowledges the receipt of the data.

4. Control mode: The strobe is inhibited internally.

ARDY

on the mode of operation selected for Port A as follows:

1. Output mode: This signal goes active to indicate that the Port A

output register has been loaded and the peripheral data bus is stable

and ready for transfer to the peripheral device.

2. Input mode: This signal is active when the Port A input register is

empty and is ready to accept data from the peripheral device.

3. Bidirectional mode: This signal is active when data is available in the

Port A output register for transfer to the peripheral device. In this

mode, data is not placed on the Port A data bus unless ASTB is active.

4. Control mode: This signal is disabled and forced to a Low state.

B7-B0

Port B Bus (bidirectional, tristate). This 8-bit bus is used to transfer data

and/or status or control information between Port B of the PIO and a

peripheral device. The Port B data bus is capable of supplying 1.5 mA @

1.5V to drive Darlington transistors. B0 is the least significant bit of the bus.

BSTB

Port B Strobe Pulse from Peripheral Device (input, active Low). The

meaning of this signal is similar to that of ASTB with the following

exception: In the Port A bidirectional mode, this signal strobes data from

the peripheral device into the Port A input register.

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Zilog Z08470 Manual de usuario Pagina 203