921

HS-82C37ARH

A4-A7

37-40

O

Address: The four most significant address lines are three-state outputs and provide 4 bits of address.

These lines are enabled only during the Active cycle.

HRQ

10

O

Hold Request: The Hold Request (HRQ) output is used to request control of the system bus. When a

DREQ occurs and the corresponding mask bit is clear, or a software DMA request is made, the HS-

82C37ARH issues HRQ. The HLDA signal then informs the controller when access to the system bus-

ses is permitted. For stand-alone operation where the HS-82C37ARH always controls the busses, HRQ

may be tied to HLDA. This will result in one S0 state before the transfer.

DACK0-

DACK3

14,15, 24,

25

O

DMA Acknowledge: DMA acknowledge is used to notify the individual peripherals when one has been

granted a DMA cycle. The sense of these lines is programmable. Reset initializes them to active low.

AEN

9

O

Address Enable: Address Enable enables the 8-bit latch containing the upper 8 address bits onto the

system address bus. AEN can also be used to disable other system bus drivers during DMA transfers.

AEN is active HIGH.

ADSTB

8

O

Address Strobe: This is an active high signal used to control latching of the upper address byte. It will

drive directly the strobe input of external transparent octal latches, such as the 82C82. During block op-

erations, ADSTB will only be issued when the upper address byte must be updated, thus speeding op-

eration through elimination of S1 states. (See Note 2).

MEMR

3

O

Memory Read: The Memory Read signal is an active low three-state output used to access data from

the selected memory location during a DMA Read or a Memory-to-Memory transfer.

MEMW

4

O

Memory Write: The Memory Write is an active low three-state output used to write data to the selected

memory location during a DMA Write or a Memory-to-Memory transfer.

NC

5

No connect. Pin 5 is open and should not be tested for continuity.

SYMBOL

PIN

NUMBER

TYPE

DESCRIPTION

Spec Number

518058