Maxim Integrated DS4830A Optical Microcontroller - Manual (Page 117)

DS4830A User’s Guide
117
12.4.3.2 – SPI Configuration Register (SPICF_M)
Bit
7 6 5 4 3 2 1 0
Name ESPII SAS - - - CHR CKPHA CKPOL
Reset 0 0 0 0 0 0 0 0
Access rw rw r r r rw rw rw
BIT NAME DESCRIPTION
7 ESPII SPI Interrupt Enable. Setting this bit to ‘1’ enables the SPI interrupt when MODF,
WCOL, ROVR or SPIC flags are set. Clearing this bit to ‘0’ disables the SPI interrupt.
6 SAS Slave Active Select.
In Master mode, this is used only when mode fault is enabled.
If SAS = 0, then mode fault is detected when active low is detected on MSPICS pin.
If SAS = 1, then mode fault is detected when active high is detected on MSPICS pin.
5:3 Reserved Reserved, Read Returns 0.
2 CHR Character Length Bit. The CHR bit determines the character length for an SPI
transfer cycle. A character can consist of 8 or 16 bits in length. When CHR bit is ‘0’, the
character is 8 bits; when CHR is set to ‘1’, the character is 16 bits.
1 CKPHA SPI Clock Phase Select. This bit is used with the CKPOL bit to determine the SPI
transfer format. When the CKPHA is set to ‘1’, the SPI will sample input data at an
inactive edge. When the CKPOL is cleared to 0, the SPI will sample input at an active
edge.
0 CKPOL SPI Clock Polarity Select. This bit is used with the CKPHA bit to determine the SPI
transfer format. When the CKPOL is set to ‘1’, the SPI uses the clock falling edge
as an active edge. When the CKPOL is cleared to 0, the SPI selects the clock rising
edge as an active edge.
12.4.3.3 – SPI Clock Register (SPICK_M)
Bit 7 6 5 4 3 2 1 0
Name SPICK_M[7:0]
Reset 0 0 0 0 0 0 0 0
Access rw rw rw rw rw rw rw rw
BIT NAME DESCRIPTION
7:0 SPICK_M[7:0] Clock Divide Ratio Bits. These bits select one of the 256 divide ratios (0 to 255) used for
the baud rate generator, with bit 7 as the most significant. The frequency of SPI baud rate
is calculated using the following equation:
SPI Baud Rate = ½ x Core Clock / (SPICK[7:0] + 1)
12.4.3.4 – SPI Data Buffer Register (SPIB_M)
Bit 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0
Name SPIB_M[15:0]
Reset 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
Access* rw rw rw rw rw rw rw rw rw rw rw rw rw rw rw rw
*Unrestricted read, write is allowed outside of a transfer cycle; when the STBY bit is set, write is blocked and will
cause write collision error.
BIT NAME DESCRIPTION
15:0 SPIB_M[15:0] SPI Data Buffer Bits. Data for SPI is read from or written to this location. The serial
transmit and receive buffers are separate but both are addressed at this location.