SC16IS752IPW datasheet(29/59 Pages) NXP

29 / 59 page

SC16IS752_SC16IS762_7

Product data sheet

Rev. 07 — 19 May 2008

29 of 59

NXP Semiconductors

SC16IS752/SC16IS762

Dual UART with I2C-bus/SPI interface, 64-byte FIFOs, IrDA SIR

8.11 Transmission Control Register (TCR)

This 8-bit register is used to store the RX FIFO threshold levels to stop/start transmission

during hardware/software ﬂow control. Table 22 shows Transmission Control Register bit

settings. If TCR bits are cleared, then selectable trigger levels in FCR are used in place of

TCR.

TCR trigger levels are available from 0 bytes to 60 characters with a granularity of four.

Remark: TCR can only be written to when EFR[4] = logic 1 and MCR[2] = logic 1. The

programmer must program the TCR such that TCR[3:0] > TCR[7:4]. There is no built-in

hardware check to make sure this condition is met. Also, the TCR must be programmed

with this condition before Auto-RTS or software ﬂow control is enabled to avoid spurious

operation of the device.

8.12 Trigger Level Register (TLR)

This 8-bit register is used to store the transmit and received FIFO trigger levels used for

interrupt generation. Trigger levels from 4 to 60 can be programmed with a granularity

of four. Table 23 shows Trigger Level Register bit settings.

Remark: TLR can only be written to when EFR[4] = logic 1 and MCR[2] = logic 1. If

TLR[3:0] or TLR[7:4] are logical 0, the selectable trigger levels via the FIFO Control

from 4 characters to 60 characters are available with a granularity of four. The TLR should

be programmed for N

⁄

4, where N is the desired trigger level.

When the trigger level setting in TLR is zero, the SC16IS752/SC16IS762 uses the trigger

level setting deﬁned in FCR. If TLR has non-zero trigger level value, the trigger level

deﬁned in FCR is discarded. This applies to both transmit FIFO and receive FIFO trigger

level setting.

When TLR is used for RX trigger level control, FCR[7:6] should be left at the default state

‘00’.

Table 22.

Transmission Control Register bits description

Bit

Symbol

Description

7:4

TCR[7:4]

RX FIFO trigger level to resume

3:0

TCR[3:0]

RX FIFO trigger level to halt transmission

Table 23.

Trigger Level Register bits description

Bit

Symbol

Description

7:4

TLR[7:4]

RX FIFO trigger levels (4 to 60), number of characters available

3:0

TLR[3:0]

TX FIFO trigger levels (4 to 60), number of spaces available

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