
XRT79L71
REV. P1.0.3
PRELIMINARY
1 - CHANNEL DS3/E3 ATM UNI/PPP COMBO IC
á
6
J16
J15
J14
PTYPE_0
PTYPE_1
PTYPE_2
I
Microprocessor Type Select input:
These three input pins are used to configure the Microprocessor Interface block to
readily support a wide variety of Microprocessor Interfaces. The relationship
between the settings of these input pins and the corresponding Microprocessor Inter-
face configuration is presented below.
J13
DBEN
I
Bi-directional Data Bus Enable Input pin:
If the Microprocessor Interface is operating in the Intel-I960 Mode, then this input pin
is used to enable the Bi-directional Data Bus.
Setting this input pin "Low" enables the Bi-directional Data bus. Setting this input
"High" tri-states the Bi-directional Data Bus.
B15
BLAST
I
Last Burst Transfer Indicator input pin:
If the Microprocessor Interface is operating in the Intel-I960 Mode, then this input pin
is used to indicate to the Microprocessor Interface block that the current data transfer
is the last data transfer within the current burst operation.
The Microprocessor should assert this input pin by toggling it "Low" in order to
denote that the current READ or WRITE operation within a BURST operation is the
last operation of this BURST operation.
H13
Direct_Ad
I
Direct Address Select pin:
This input pin is used to select the addressing mode for the Microprocessor Interface
block.
Setting this pin "High" will put the Microprocessor Interface block of the XRT79L71
into Direct Addressing Mode.
In Direct Addressing Mode, all 15 address pins (A0 - A14) are used to select the on-
chip Framer/UNI registers and RAM space for READ and WRITE Operations with the
Microprocessor.
N
OTE
:
It is recommended to set this pin "High" and access the Microprocessor
Interface block using the Direct Addressing Mode.
Setting this pin "Low" will put the Microprocessor Interface block of the XRT79L71
into Indirect Addressing Mode.
In Indirect Addressing mode, only the lower 8 address pins (A0 - A7) are used to
select the on-chip Framer/UNI registers and RAM space for READ and WRITE Oper-
ations with the Microprocessor. Two microprocessor accesses are needed to READ
or WRITE to the on-chip Framer/UNI registers and RAM space.
PIN DESCRIPTIONS
P
IN
#
N
AME
TYPE
D
ESCRIPTION
PTYPE[2:0]
010
001
Asynchronous Intel
Intel I960, Motorola MPC860
011
Intel X86
100
IBM Power PC
IDT3051/52 (MIPS)
101
Asynchronous Motorola
000
Microprocessor Interface Mode