XR21B1421 Datasheet, PDF (42/50 Pages) Exar Corporation – Enhanced 1-Ch Full-Speed

XR21B1421
Field
SUSPEND_STATE_MSB
SUSPEND_STATE_LSB
SUSPEND_MODE_MSB
SUSPEND_MODE_LSB
RS485_POL
CLKOUT_DIV
Offset
14
15
Size
1
1
16
1
17
1
18
1
19
1
Value
See Table 28
See Table 29
Description
GPIO State During Suspend
(when USE_SUSPEND is set)
0: All GPIO pins asserted low in USB Suspend state
1: All GPIO pins asserted high in USB Suspend state
GPIO Mode During Suspend
(when USE_SUSPEND is set)
0: GPIO pin is Open Drain when is USB Suspend state
1: GPIO pin is Push-pull when is USB Suspend state
Auto RS-485 half-duplex polarity
0: auto RS-485 half-duplex enable active low
1: auto RS-485 half-duplex enable active high
Output clock frequency
8-bit value sets output clock frequency divider. Freq out = 2 MHz / 2 x CLK-
OUT_DIV
Default configuration for each pin is shown in Table 30.
Table 22: CLK, CTS, RS485, TXT, RXT, DSR Pin Bit Positions
Bit
Description
7 PULL_U
0: disable pull-up resistor
1: enable pull-up resistor
6 PULL_D
0: disable pull-down resistor
1: enable pull-down resistor if pull-up is not enabled as well
5:2 Reserved
1:0 CONFIG
00: GPIO Input
01: GPIO Open drain output
10: GPIO Push-pull output
11: CLK, RS485, TXT, RXT functionality outputs, CTS, DSR functional-
ity inputs
If CTS or DSR functions are selected, RTS and DTR functions (respec-
tively) must also be selected and DTR and RTS functions (respectively)
must be configured as GPIOs.
© 2014 Exar Corporation
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exar.com/XR21B1421
Rev 1B