MA28155

10/20

OPERATING MODE 2

(Strobed Bidirectional Bus I/0)

This functional configuration provides a means for

communicating with a peripheral device or structure on a

single 8-bit bus for both transmitting and receiving data

(bidirectional bus l/O) . Handshaking signals are provided to

maintain proper bus flow discipline in a similar manner to Mode

1, Interrupt generation and enable/disable functions are also

available.

s Used in group A only.

s One 8-bit bidirectional bus port (port A) and 5-bit control

port (port C).

s Both inputs and outputs are latched,

s The 5-bit control port (port C) is used for control and status

of the 8-bit bidirectional bus port (port A).

NOTE:

Any sequence where RD/WN = 0 coincident with DSN low occurs before ACKN and STBN occurs before RD/WN = 1

coincident with DSN is permissable

(INTR = IBF MASK STBN (RD/WN = 1. DSN = 0) + OBFN MASK ACKN (RD/WN = 0. DSN = 0))

Figure 15: Bidirectional Timing Diagram

DSN

RD/WN

OBFN

ACKN

STBN