XR16V654_0709 Datasheet, PDF (40/58 Pages) Exar Corporation – 2.25V TO 3.6V QUAD UART WITH 64-BYTE FIFO

XR16V654/654D
2.25V TO 3.6V QUAD UART WITH 64-BYTE FIFO
REV. 1.0.2
EFR[6]: Auto RTS Flow Control Enable
RTS# output may be used for hardware flow control by setting EFR bit-6 to logic 1. When Auto RTS is
selected, an interrupt will be generated when the receive FIFO is filled to the programmed trigger level and
RTS de-asserts HIGH at the next upper trigger level/hysteresis level. RTS# will return LOW when FIFO data
falls below the next lower trigger level/hysteresis level. The RTS# output must be asserted (LOW) before the
auto RTS can take effect. RTS# pin will function as a general purpose output when hardware flow control is
disabled.
• Logic 0 = Automatic RTS flow control is disabled (default).
• Logic 1 = Enable Automatic RTS flow control.
EFR[7]: Auto CTS Flow Control Enable
Automatic CTS Flow Control.
• Logic 0 = Automatic CTS flow control is disabled (default).
• Logic 1 = Enable Automatic CTS flow control. Data transmission stops when CTS# input de-asserts to logic
1. Data transmission resumes when CTS# returns to a logic 0.
4.13 Software Flow Control Registers (XOFF1, XOFF2, XON1, XON2) - Read/Write
These registers are used as the programmable software flow control characters xoff1, xoff2, xon1, and xon2.
For more details, see Table 8.
4.14 FIFO Status Register (FSTAT) - Read/Write
This register is applicable only to the 100 pin QFP XR16V654. The FIFO Status Register provides a status
indication for each of the transmit and receive FIFO. These status bits contain the inverted logic states of the
TXRDY# A-D outputs and the (un-inverted) logic states of the RXRDY# A-D outputs. The contents of the
FSTAT register are placed on the data bus when the FSRS# pin (pin 76) is a logic 0. Also see FSRS# pin
description.
FSTAT[3:0]: TXRDY# A-D Status Bits
Please see Table 5 for the interpretation of the TXRDY# signals.
FSTAT[7:4]: RXRDY# A-D Status Bits
Please see Table 5 for the interpretation of the RXRDY# signals.
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