3

Pin Descriptions

SYMBOL

PIN

NUMBER

TYPE

DESCRIPTION

VDD

31

VDD: is the +5V power supply pin. A 0.1

µF capacitor between pins 31 and 20 is recommended for

decoupling.

GND

20

Ground

CLK

12

I

CLOCK INPUT: The Clock Input is used to generate the timing signals which control HS-82C37ARH

operations. This input may be driven from DC to 5MHz and may be stopped in either high or low state for

standby operation.

CS

11

I

CHIP SELECT: Chip Select is an active low input used to enable the controller onto the data bus for CPU

communications.

RESET

13

I

RESET: This is an active high input which clears the Command, Status, Request and Temporary Registers,

the First/Last Flip-Flop, and the Mode Register Counter. The Mask Register is Set to ignore requests.

Following a Reset, the controller is in an idle cycle.

READY

6

I

READY: This signal can be sued to extend the memory read and write pulses from the HS-82C37ARH to

accommodate slow memories or I/O devices. Ready must not make transitions during its specified set-up and

hold times. Ready is ignored in Verify Transfer mode.

HLDA

7

I

HOLD ACKNOWLEDGE: The active high Hold Acknowledge from the CPU indicates that is has relinquished

control of the system busses.

DREQ0-

DREQ3

16-19

I

DMA REQUEST: The DMA Request (DREQ) lines are individual asynchronous channel request inputs used

by peripheral circuits to obtain DMA service. In Fixed Priority, DREQ0 has the highest priority and DREQ3

has the lowest priority. A request is generated by activating the DREQ line of a channel. DACK will

acknowledge the recognition of DREQ signal. Polarity of DREQ is programmable. Reset initializes these lines

to active. DREQ will not be recognized while the clock is stopped. Unused DREQ inputs should be pulled

High or Low (inactive) and the corresponding mask bit set.

DB0-DB7

21-23

26-30

I/O

DATA BUS: The Data Bus lines are bidirectional three-state signals connected to the system data bus. The

outputs are enabled in the Program Condition during the I/O Read to output the contents of a register to the

CPU. The outputs are disabled and the inputs are read during an I/O Write cycle when the CPU is

programming the HS-82C37ARH Control Registers. During DMA cycles, the most significant 8 bits of the

address are output onto the data bus to be strobed into an external latch by ADSTB. In Memory-to-Memory

operations, data from the memory enters the HS-82C37ARH on the data bus during the read-from-memory

transfer, then during the write-to-memory transfer, the data bus outputs write the data into the new memory

location.

IOR

1

I/O

I/O READ: I/O Read is a bidirectional active low three-state line. In the Idle cycle, it is an input control signal

used by the CPU to read the internal registers. In the Active cycle, it is an output control signal used by the

HS-82C37ARH to access data from a peripheral during a DMA Write transfer.

IOW

2

I/O

I/O WRITE: I/O Write is a bidirectional active low three-state line. In the Idle cycle, it is an input control signal

used by the CPU to load information into the HS-82C37ARH. In the Active cycle, it is an output control signal

used by the HS-82C37ARH to load data to the peripheral during a DMA Read transfer.

EOP

36

I/O

END OF PROCESS: End of Process (EOP) is an active low bidirectional signal. Information concerning the

completion of DMA services is available at the bidirectional EOP pin.

The HS-82C37ARH allows an external signal to terminate an active DMA service by pulling the EOP pin low.

A pulse is generated by the HS-82C37ARH when terminal count (TC) for any channel is reached, except for

channel 0 in Memory-to-Memory mode. During Memory-to-Memory transfers, EOP will be output when the

TC for channel 1 occurs.

The EOP pin is driven by an open drain transistor on-chip, and requires an external pull-up resistor.

When an EOP pulse occurs, whether internally or externally generated, the HS-82C37ARH will terminate the

service, and if Autoinitialize is enabled, the base registers will be written to the current registers of that

channel. The mask bit and TC bit in the Status Register will be set for the currently active channel by EOP

unless the channel is programmed for Autoinitialize. In that case, the mask bit remains clear.

A0-A3

32-35

I/O

Address: The four least significant address lines are bidirectional three-state signals. In the Idle cycle, they

are inputs and are used by the HS-80C86RH to address the internal registers to be loaded or read. In the

Active cycle, they are outputs and provide the lower 4 bits of the output address.

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.

HS-82C37ARH