Digital interfaces

STLC2500A

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7

Digital interfaces

7.1

The UART interface

The STLC2500A contains a 4-pin (UART_RXD, UART_TXD, UART_RTS, and UART_CTS)

UART compatible with 16450, 16550 and 16750 standards. It is running up to 1842 kbps

(+1.5%/-1%).

The configuration is 8 data bits, 1 start bit, 1 stop bit, and no parity bit. 128-byte FIFO with

configurable threshold interrupts for low CPU load and high throughput. Auto RTS/CTS is

implemented in HW, controllable by SW.

The UART accepts all HCI commands as described in the Bluetooth specification, it

supports H4 proprietary commands and the 4-wire UART sleep mode. The complete list of

supported proprietary HCI commands is available in the STLC2500A Software Interface

document.

Table 19 contains the list of supported baud rates selectable by HCI commands. The default

baud rate is 115200 [bps].

7.2

The PCM interface

The chip contains a 4-pin (PCM_CLK, PCM_SYNC, PCM_A, and PCM_B) direct voice

interface to connect to standard CODEC including internal decimator and interpolator filters.

The implementation is compliant with the MP-PCM requirements for voice transfer (8 kHz

PCM_SYNC and 8 or 16 bits data).

The four signals of the PCM interface are:

–

PCM_CLK:

PCM clock

–

PCM_SYNC:

PCM 8 kHz sync (every 125

µs)

–

PCM_A:

PCM data

–

PCM_B:

PCM data

The data can be linear PCM (13-16 bit),

µ-Law (8 bit) or A-Law (8bit). The interface can be

programmed as Master or as Slave via specific HCI commands.

Two additional PCM_SYNC signals can be provided via the GPIOs. See

Section 7.4 for

more details.

Table 19.

List of supported baud rates

Baud rate

Baud rate (contined)

Baud rate (contined)

1842 k

57.6 k

4800

921.6 k

38.4 k

2400

460.8 k

28.8 k

1800

230.4 k

19.2 k

1200

153.6 k

14.4 k

900

115.2 k (default)

9600

600

76.8 k

7200

300