34C60 datasheet(49/58 Pages) SMSC

49 / 58 page

SMSC DS – PPC34C60

Page 49

Rev. 06/01/2001

ADVANCED INFORMATION

FIGURE 20 - ECP REVERSE DATA TRANSFER TIMING

(ECP DATA READ, PARALLEL PORT SIGNALS)

Note: The optional use of the nERR (nFAULT) line to "hint" to the Host that the peripheral has data to send to the Host is

not supported in the PPC34C60. The driver should ignore any activity on this line. The PPC34C60 supports reverse data

transfers only (not reverse command transfers) and, therefore, always asserts the BSY (nCMD) signal during reverse

transfers.

See ECP Reverse Data Transfer Timing Parameters.

ECP REVERSE DATA TRANSFER TIMING (ECP DATA READ, PARALLEL PORT SIGNALS)

PARAMETER

MIN

TYP

MAX

UNITS

To prepare for an ECP reverse channel transfer the Host tri-

states the parallel data lines HD[0:7] and asserts nALF at the

same time. Next the Host asserts nINIT to initiate an ECP bus

reversal. The PPC34C60 requires this amout of time between

these events.

The PPC34C60 acknowledges the bus reversal by

deasserting the PE signal. At this point in time the parallel port

bus is in the reverse idle state.

208

[5 SCLK]

334

[8 SCLK]

Along with deasserting the PE signal the PPC34C60 takes

control of the parallel port data bus HD[0:7]. The data on this

bus remains undefined until the PPC34C60 has accessed and

placed a data byte on the bus. Along with driving the data lines

with valid data, the PPC34C60 asserts BSY to indicate that

this is a data transfer.

1,084

[13

BCLK]

After placing data on the parallel port data lines the

PPC34C60 asserts nACK to inform the Host that valid data is

available.

125

[3 SCLK]

167

[4 SCLK]

Next, the Host will acknowledge that it is ready for the data by

deasserting nALF.

infinite

Now the PPC34C60 will deassert nACK in response to the

Host. The Host will latch the data on HD[0:7] on this rising

edge of nACK.

125

[3 SCLK]

167

[4 SCLK]

The Host completes the ECP reverse transfer, acknowledging

that it has accepted the data byte by asserting nALF.

50ns

VALID DATA

t11

t10

HD[0:7]

nSTB H

nALF H

nSEL H

nINIT H

BSY P

nACK P

PE P

SLCT P

nERR P

DATA

34C60 Datasheet(PDF) 49 Page - SMSC Corporation

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