ST16C2552CJ44 EXAR [Exar Corporation], ST16C2552CJ44 Datasheet - Page 13

• Manufacturer Part Number: ST16C2552CJ44
• Description: 2.97V TO 5.5V DUAL UART WITH 16-BYTE FIFO
• Manufacturer: EXAR [Exar Corporation]

REV. 4.2.1
reported in the LSR register bits 2-4. Upon unloading the receive data byte from RHR, the receive FIFO pointer
is bumped and the error tags are immediately updated to reflect the status of the data byte in RHR register.
RHR can generate a receive data ready interrupt upon receiving a character or delay until it reaches the FIFO
trigger level. Furthermore, data delivery to the host is guaranteed by a receive data ready time-out interrupt
when data is not received for 4 word lengths as defined by LCR[1:0] plus 12 bits time. This is equivalent to 3.7-
4.6 character times. The RHR interrupt is enabled by IER bit-0.
The Receive Holding Register is an 8-bit register that holds a receive data byte from the Receive Shift
Register. It provides the receive data interface to the host processor. The RHR register is part of the receive
FIFO of 16 bytes by 11-bits wide, the 3 extra bits are for the 3 error tags to be reported in LSR register. When
the FIFO is enabled by FCR bit-0, the RHR contains the first data character received by the FIFO. After the
RHR is read, the next character byte is loaded into the RHR and the errors associated with the current data
byte are immediately updated in the LSR bits 2-4.
F
F
2.11.1
IGURE
IGURE
9. R
10. R
Receive Holding Register (RHR) - Read-Only
ECEIVER
ECEIVER
Receive Data
Byte and Errors
16 bytes by 11-bit
16X Clock
16X Clock
and Errors
Data Byte
wide FIFO
O
Receive
O
PERATION IN NON
PERATION IN
Receive Data Shift
LSR bits
Register (RSR)
FIFO M
Tags in
Error
4:2
-FIFO M
RX FIFO
RHR
Receive Data Shift
Register (RSR)
ODE
Holding Register
Receive Data
ODE
(RHR)
Validation
Data Bit
13
2.97V TO 5.5V DUAL UART WITH 16-BYTE FIFO
Validation
RHR Interrupt (ISR bit-2) when FIFO fills
up to trigger level.
FIFO is Enabled by FCR bit-0=1
Data Bit
RHR Interrupt (ISR bit-2)
Receive Data Characters
Receive Data Characters
RXFIFO1
RXFI
ST16C2552