SC16C652 datasheet(17/41 Pages) PHILIPS

17 / 41 page

Philips Semiconductors

SC16C652

Dual UART with 32 bytes of transmit and receive FIFOs

Product data

Rev. 04 — 20 June 2003

17 of 41

9397 750 11634

7.2.2

IER versus Receive/Transmit FIFO polled mode operation

When FCR[0] = logic 1, resetting IER[0-3] enables the SC16C652 in the FIFO polled

mode of operation. In this mode, interrupts are not generated and the user must poll

the LSR register for TX and/or RX data status. Since the receiver and transmitter

have separate bits in the LSR either or both can be used in the polled mode by

selecting respective transmit or receive control bit(s).

• LSR[0] will be a logic 1 as long as there is one byte in the receive FIFO.

• LSR[1-4] will provide the type of receive errors, or a receive break, if encountered.

• LSR[5] will indicate when the transmit FIFO is empty.

• LSR[6] will indicate when both the transmit FIFO and transmit shift register are

empty.

• LSR[7] will show if any FIFO data errors occurred.

7.3 FIFO Control Register (FCR)

This register is used to enable the FIFOs, clear the FIFOs, set the receive FIFO

trigger levels, and select the DMA mode.

7.3.1

DMA mode

Mode 0 (FCR bit 3 = 0): Set and enable the interrupt for each single transmit or

receive operation, and is similar to the 16C450 mode. Transmit Ready (TXRDY) will

go to a logic 0 whenever the FIFO (THR, if FIFO is not enabled) is empty. Receive

Ready (RXRDY) will go to a logic 0 whenever the Receive Holding Register (RHR) is

loaded with a character.

Mode 1 (FCR bit 3 = 1): Set and enable the interrupt in a block mode operation. The

transmit interrupt is set when the transmit FIFO is below the programmed trigger

level. The receive interrupt is set when the receive FIFO ﬁlls to the programmed

trigger level. However, the FIFO continues to ﬁll regardless of the programmed level

until the FIFO is full. RXRDY remains a logic 0 as long as the FIFO ﬁll level is above

the programmed trigger level.

SC16C652 Datasheet(PDF) 17 Page - NXP Semiconductors