XR16C872CQ EXAR [Exar Corporation], XR16C872CQ Datasheet - Page 44

• Manufacturer Part Number: XR16C872CQ
• Description: DUAL UART WITH 1284 PARALLEL PORT AND PLUG-AND-PLAY CONTROLLER
• Manufacturer: EXAR [Exar Corporation]

XR16C872
“ECP MODE” SIGNAL DESCRIPTIONS
ECP Mode Forward Data and Command Transfer Cycle
1. Host places data on the data lines and indicates a data cycle by setting HostAck high.
2. Host asserts HostClk low to indicate valid data.
3. Peripheral acknowledge host by setting PeriphAck high.
4. Host sets HostClk high. This is the edge that should be used to clock the data in to the peripheral.
5. Peripheral sets PeriphAck low to indicate that it is ready for the next byte.
6. The cycle repeats, but this time it is command cycle because HostAck is low.
ECP Mode Reverse Data and Command Transfer Cycle
1. The Host requests a reverse channel transfer by setting ReverseReq# low.
2. The peripheral signals that it is okay to proceed by setting AckReverse# low.
3. The peripheral places data on the data lines and indicates a data cycle by setting PeriphAck high.
4. Peripheral asserts PeriphClk low to indicate valid data.
5. Host acknowledges by setting HostAck high.
6. Peripheral sets PeriphClk high. This is the edge that should be used to clock the data in to the host.
7. Host sets HostAck low to indicate that it is ready for the next byte.
8. The cycle repeats, but this time it is a Command cycle because PeriphAck is low.
Signal
Name
STROBE#
AUTOFD#
SELCTIN#
INIT#
ACK#
BUSY
PE
SELECT
ERR#
PD0-PD7
Rev. 1.00
Signal
Type
I/O
O
O
O
O
I
I
I
I
I
ReverseReq#
AckReverse#
PeriphReq#
ECP mode
1284Active
PeriphAck
PeriphClk
HostAck
HostClk
D0-D7
Name
Xflag
DISCONTINUED
Description
Used with PeriphAck to transfer data or address information in
the forward direction.
Provides Command / Data status in the forward direction. Used
with PeriphClk to transfer data in the reverse direction.
Set high when host is in a 1284 transfer mode.
Driven low to put the channel in reverse direction.
Used with HostAck to transfer data in the reverse direction.
Used with HostClk to transfer data or address information in the
forward direction. Provides Command / Data status in the reverse
direction.
Driven low to acknowledge ReverseRequest.
Extensibility flag.
Set low by peripheral to indicate that reverse dat is available.
Bi-directional data lines.
44
Visit Exar Web Site at www.exar.com