XR68C92_05 Datasheet, PDF (4/33 Pages) Exar Corporation – DUAL UNIVERSAL ASYNCHRONOUS RECEIVER AND TRANSMITTER

XR68C92/192
SYMBOL DESCRIPTION (* 44 pin LQFP)
Symbol
-RESET
A0-A3
-IACK
-DACK
-CS
D0-D7
R/-W
-INT
XTAL1
Pin
Signal
44 40 44* type
Pin Description
38 34 32
I
2,4, 1,3, 40,42,
6,7 5,6 44,1 I
Master Reset (active low). A low on this pin will reset all the
outputs and internal registers. The transmitter output and
the receiver input will be disabled during reset time.
Address select lines. To select internal registers.
41 37 35
I Interrupt acknowledge (active low). A low on this pin indicates
that the CPU has received an interrupt. If not used, this pin
should be tied to VCC.
10
9
4
O Data Transfer Acknowledge ( three-state active low output).
A low on this pin indicates proper transfer of data between
the CPU and XR68C92/192 during read, write and interrupt
cycles.
39 35 33
I Chip select (active low). A low at this pin enables the data
bus transfer operation.
28,18 25,16 22,12
Bi-directional data bus. Eight bit, three state data bus to
27,19 24,17 21,13 I/O transfer information to or from the CPU. D0 is the least
26,20 23,18 20,14
significant bit of the data bus and the first serial data bit to be
25,21 22,19 19,15
received or transmitted.
9
8
3
I Read/Write strobe. When -CS is asserted, a high on this pin
transfers the contents of the XR68C92/192 data bus to the
CPU, and a low on this pin will transfer the contents of the
CPU data bus to the addressed register.
24 21 18
O Interrupt output (open drain, active low) This pin goes low
upon occurrence of one or more of eight maskable interrupt
conditions (when enabled by the interrupt mask register).
CPU can read the interrupt status register to determine the
interrupting condition(s). This output requires a 10k ohms
pull-up resistor.
36 32 30
I Crystal input 1 or external clock input. A crystal can be
connected between this pin and XTAL2 pin to utilize the
internal oscillator circuit. An external clock can be used to
clock internal circuit and baud rate generator for custom
transmission rates.
Rev. 1.33
4