82091AA Datasheet, PDF (22/204 Pages) Intel Corporation – ADVANCED INTEGRATED PERIPHERAL (AIP)

82091AA
2 6 2 NIBBLE PROTOCOL SIGNAL DESCRIPTION
The Nibble protocol assigns the following signal operation to the parallel port pins The name in bold at the
beginning of the signal description column is the Nibble protocol signal name The terms assert and negate
are used in accordance with the 82091AA signal name as described at the beginning of Section 2 0 For
example AUTOFD (HostBusy) asserted refers to AUTOFD (HostBusy) at a low level
82091AA
Signal
Name
STROBE
BUSY
ACK
SELECT
PERROR
FAULT
INIT
AUTOFD
PD 7 0
SELECTIN
Type
Nibble Protocol Signal Name and Description
O STROBE The host controls this signal via the PCON Register and STROBE
should be held negated by the host
I
PRINTER BUSY (PtrBusy) The peripheral drives this signal to transfer data bits
3 and 7 sequentially The status of this signal line is reported in the PSTAT
Register
I
PRINTER CLOCK (PtrClk) The peripheral device asserts ACK (PtrClk) to
indicate to the host that data is available The signal is subsequently asserted to
qualify data being sent to the host The status of this signal line is reported in the
PSTAT Register If interrupts are enabled via the PCON Register the assertion of
this signal causes a host interrupt to be generated
I
XFLAG The peripheral device drives this signal to transfer data bits 1 and 5
sequentially The status of this signal line is reported in the PSTAT Register
I
ACKNOWLEDGE DATA REQUEST (AckDataReq) This signal is initially high
The peripheral device drives this signal low to acknowledge HostBusy assertion
PERROR is subsequently used to transfer data bits 2 and 6 sequentially The
status of this signal line is reported in the PSTAT Register
I
DATA AVAILABLE (DataAvail) The peripheral device asserts FAULT
(DataAvail) to indicate data availability Subsequently used to transfer data bits 0
and 4 sequentially The status of this signal line is reported in the PSTAT
Register
O INITIALIZE The host controls this signal via the PCON Register
O HOST BUSY (HostBusy) The host negates AUTOFD (HostBusy) in response
to ACK being asserted This signal is subsequently driven low to enable the
peripheral to transfer data to the host AUTOFD is then driven high to
acknowledge receipt of byte data This signal is controlled via the PCON
Register
O DATA This 8-bit output data path to the peripheral Host data is written to the
peripheral attached to the parallel port interface on these signal lines
O SELECT INPUT This signal is controlled by the PCON Register
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