XR28V382 Datasheet, PDF (8/39 Pages) Exar Corporation – 3.3V DUAL LPC UART WITH 128-BYTE FIFO

XR28V382
3.3V DUAL LPC UART WITH 128-BYTE FIFO
REV. 1.0.1
1.2.1.1 Start Frame
The Start frame indicates begining of the SERIRQ cycle. During this frame the SERIRQ is driven LOW for 4-8
clock cycles. It can be initiated by the host or V382 depending on the mode of operation.
In the Continuous mode, only the host controller initiates the Start frame to update the SERIRQ line
information. The host controller drives the SERIRQ signal low for 4 to 8 clock periods. Upon a reset, the
SERIRQ signal defaults to the Continuous mode for the host controller to initiate the first Start frame.
In the Quiet mode, the Start frame is initiated by the device/host. The V382 drives the SERIRQ signal active
low for one clock to initiate a Start Frame, and then tri-states it immediately. The host controller will then take
over driving SERIRQ signal low in the next clock and will continue driving the SERIRQ low for 3 to 7 clock
periods. This makes the total number of clocks low for 4 to 8 clock periods. After these clocks, the host
controller will drive the SERIRQ high for one clock and then tri-states it.
A Start Frame may not be initiated while SERIRQ is active. The SERIRQ is active between Start and Stop
frames while it is idle between Stop and Start frames.
1.2.1.2 IRQ Frame
Once the start frame has been initiated, all the peripherals must start counting frames based on the rising edge
of the clock (LCLK). Each IRQ Frame is three clocks: Sample phase, Recovery phase, and Turn-around phase.
During the Sample phase, the peripheral drives SERIRQ low if the corresponding IRQ is active. If the
corresponding IRQ is inactive, then SERIRQ will be left tri-stated. During the Recovery phase, the peripheral
device drives the SERIRQ high. During the Turn-around phase, the peripheral device leaves the SERIRQ tri-
stated. The V382 supports IRQ3, IRQ4, IRQ5, IRQ7, IRQ9, IRQ10, and IRQ11.
TABLE 4: SERIRQ SAMPLING PERIODS
IRQ/DATA FRAME
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
32:22
SIGNAL SAMPLED
IRQ0
IRQ1
SMI#
IRQ3
IRQ4
IRQ5
IRQ6
IRQ7
IRQ8
IRQ9
IRQ10
IRQ11
IRQ12
IRQ13
IRQ14
IRQ15
IOCHCK#
INTA#
INTB#
INTC#
INTD#
Unassigned
NUMBER OF CLOCKS PAST START
2
5
8
11
14
17
20
23
26
29
32
35
38
41
44
47
50
53
56
59
62
95
8