Pin Details of 8089 :
(1) AD0 to AD15 - The state of S0(bar),S1(bar),S2(bar) lines defined the function of these multiplexed
data bus line after rest these pins are float. Transfering to a 8bit data bus ,the signal ofaddress line
remain same, and are multiplexed with data D0-D15 on transfer to physical bus.(it is used with 8086)
(2) A19 -A16/ S6-S3 - When addressing memory required the A19- A16lines are active.
S6- S3 lines codded be like S6, S5, S4, S3.
S6 S5 S4 S3 Purpose
1 1 1 1 - Non-DMA cycle
1 1 1 0 - Non-DMA cycle
1 1 0 1 - DMA cycle
1 1 0 0 - DMA cycle
(3) BHE - Stands for Bus High Enable . It is used to enable data operations. On the upper half of the
data bus , a byte is transfersed then this signal is active low. Floating time of this pin is , when it is reset
and when the bus is not accuired.
(4) S0,S1,S2 : These are status pin . During any define cycle these pins are signify the I/op. Utilization
of these status line is done by bus controller to generate all the memory and input output control signal.
This pins also floated after system reset .
S1 S2 S3 function
1 1 1 passive
1 1 0 Data store
1 0 1 Data fetch
1 0 0 Instrunction fetch
0 1 1 Not used
0 1 0 Data store
0 0 1 Data fetch
0 0 0 Instrunction fetch
(5) READY - This signal is received from the addressed device. This signal indicates that the device is
reday for tarnsfering the data.
(6) LOCK - Its a output signal . The output is active low , it is set via channel control register. This
signal indicate also when the bus is needed for more than one contiguous cycle.
(7) RESET - The receipt of a Reset signal causes the IOP to suspend all its activities and enter it idle state .
(8) CLK - this clock signal provides the timming needed for all the input output operations.
(9) CA- stands for Channel Attention , This signal is input signal and active high.
(10) SEL - (select) select line is mediator between IOP & CA, because after the reset process The first
CA received informs the IOP. (Active High).
(11) DRQ1 and DRQ2(data request) : The DMA request inputs, which signal to the IOP that a
peripheral is ready to transfer and receive data using CH1,Ch2.
(12) RQ/GT- (Request grant) : In the remote mode two IOPs share same bus then This siganl utilize
the communication dialogue requird to attriutethe use of the system & I?o bus. (This signal is active
low).
(13) SINTR -1 and SINTR -2 (signal interrupt) : The interrupt signal may be sent directly to the control
proceesing unit . the signal interrupt signal output from CH1 and CH2.
(14) EXT 1 and EXT 2: (external Terminate) : (active high) The EXT signal causes the termination of
the current DMA transfer operation , if the channel is so programmed by the channel control register.