4-169

82C237

FIGURE 12. DMA TRANSFER

NOTE: For 16-bit mode, 82C237 only. In 8-bit mode this signal is always high impedance three-stated. Waveform shown is for an 8-bit transfer

with the 82C237 programmed in 16-bit mode. For a 16-bit transfer, DWLE will go low at least TASS before the falling edge of ADSTB in S2,

and remain low for the entire transfer.

TEPW (21)

TAK (9)

SI

SI

TQS

(30)

S0

S0

S1

S2

S3

S4

S2

S3

S4

SI

SI

SI

TDQ

(18)

THS

(25)

TAEL

(1)

TCLSH

(33)

TQS

(30)

TCL (13)

TCY

(14)

TCH

(12)

TDQ

(18)

TAET

(2)

TSHSL

(37)

TCLSL

(34)

TEPS

(20)

TEPH

(19)

TRHAL

(58)

TAK (9)

TAFAB (3)

TAHW (8)

TAHR (6)

TRHDI (63)

TAFC (4)

TDCTR (16)

TDCL

(15)

CLK

DREQ

HRQ

HLDA

AEN

ADSTB

DB0-DB7

A0-A7

DACK

READ

WRITE

INT EOP

EXT EOP

(64)

TAZRL

TAFDB

(5)

TFAAB

(22)

TFADB

(24)

TASS

(11)

TAHS

(7)

A8-A15

TAK

(9)

TDCL

(15)

TFAC

(23)

TDCL (15)

TDVWL

(62)

TWLWHA

(38)

TDCTW

(17)

TAVWL

(57)

TDVAL (61)

(FOR EXTENDED WRITE)

(FOR EXTENDED WRITE)

TAK (9)

TDCL

(15)

TWLWH (39)

TDCTW (17)

TWRRD

(35)

TAVRL

(56)

TRLRH

(36)

TDCTR

(16)

TAHR

(6)

TAHW

(8)

TASM

(10)

ADDRESS VALID

ADDRESS VALID

TAHS

(7)

TASS

(11)

DWLE

(SEE NOTE)