Maxim-integrated MAXQ Family Users Guide: MAXQ8913 Supplement Manual de usuario descargar pdf (Pagina 46)

MAXQ Family User’s Guide:

MAXQ8913 Supplement

11-1

ADDENDUM TO SECTION 11: SERIAL PERIPHERAL INTERFACE

(SPI) MODULE

The MAXQ8913 provides a serial peripheral interface (SPI) module, which operates as described in the MAXQ Family

User’s Guide with the following additions:

• The maximum clock rate when operating in slave mode is the system clock divided by 4.

• The SPI configuration register (SPICF) contains an additional bit, slave active select (SAS, SPICF.6). This bit allows

the sense of the slave-select input to be changed from active low (SAS = 0, default) to active high (SAS = 1).

11.1 SPI Input/Output Pins and Control Registers

Table 11-1. SPI Input and Output Pins

Table 11-2. SPI Control Registers

11.2 SPI Code Examples

11.2.1 SPI Example 1: Transmitting Data in Master Mode

move PD5.2, #1 ; Chip select for slave device

move PO5.2, #1 ; Start high

move SPICN, #03h ; Enable SPI in master mode

move SPICF, #00h ; Sample data at clock rising edge, 8 bit character

move SPICK, #63 ; SPI clock = sysclk/128

move PO5.2, #0 ; Drive chip select low

move SPIB, #12h ; Transmit byte

call waitXfer

move SPIB, #34h ; Transmit byte

call waitXfer

move PO5.2, #1 ; Release chip select

....

waitXfer:

move C, SPICN.6 ; Wait for transfer to complete

jump NC, waitXfer

move SPICN.6, #0 ; Clear transfer flag

ret

SPI INTERFACE FUNCTION PIN MULTIPLEXED WITH GPIO

SSEL: Slave Select

N8 P0.4

SCLK: Slave Clock M7 P0.5

MOSI: Master Out-Slave In L6 P0.6

MISO: Master In-Slave Out K5 P0,7

SPICN M1[02h] SPI Control Register. Enable, master/slave-mode select, and status and interrupt flags.

SPICF M1[0Ah]

SPI Configuration Register. Clock polarity/phase, character length, interrupt enable, SSEL

active-high/low mode select (SAS).

SPICK M1[0Bh] SPI Clock Register. Master baud rate = 0.5 x Sysclk/(SPICK + 1).

SPIB M1[03h] SPI Data Buffer. Writes go to the SPI write buffer; reads come from the SPI read buffer.

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Maxim-integrated MAXQ Family Users Guide: MAXQ8913 Supplement Manual de usuario Pagina 46

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