Maxim Integrated MAXQ610 - Manual (Page 91)

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MAXQ610 User’s Guide
REGISTER DESCRIPTION
SBUF1 (03h, 03h) Serial Data Buffer 1
Initialization: This buffer is cleared to 00h on all forms of reset .
Read/Write Access: Unrestricted read/write .
SBUF1.7 to SBUF1.0 Serial Data Buffer 1 Bit 7:0. Data for serial port 0 is read from or written to this location .
The serial transmit and receive buffers are separate but both are addressed at this location .
SPIB (04h, 03h) SPI Data Buffer (16-bit register)
Initialization: This buffer is cleared to 0000h on all forms of reset .
Read/Write Access: Unrestricted read, write is allowed outside of a transfer cycle; when the STBY bit is set, write
is blocked and causes write collision error .
SPIB.15 to SPIB.0 SPI Data Buffer Bits 15:0. 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 .
SPICN (05h, 03h) SPI Control Register
Initialization: This buffer is cleared to 00h on all forms of reset .
Read/Write Access: Unrestricted read/write except bit 7 is read-only .
SPICN.0 (SPIEN) SPI Enable. Setting this bit to 1 enables the SPI module and its baud-rate generator for SPI
operation . Clearing this bit to 0 disables the SPI module and its baud-rate generator .
SPICN.1 (MSTM) Master Mode Enable. MSTM functions as a master mode enable bit for the SPI module .
When MSTM is set to 1, the SPI operates as a master . When MSTM is cleared to 0, the
SPI module operates in slave mode . Note that this bit can be set from 0 to 1 only when the
SSEL signal is deasserted .
SPICN.2 (MODFE) Mode Fault Enable. When set to 1 in master mode, this bit enables the use of SSEL input
as a mode fault signal; when cleared to 0, the SSEL has no function and its port pin can be
used for other purposes . In slave mode, the SSEL pin always functions as a slave select
input signal to the SPI module, independent of the setting of the MODFE bit .
SPICN.3 (MODF) Mode Fault Flag. This bit is the mode fault flag when the SPI is operating as a master .
When mode fault detection is enabled as MODFE = 1 in master mode, a detection of a high
to low transition on the SSEL pin signifies a mode fault and sets the MODF to 1 . This bit
must be cleared to 0 by software once set . Setting this bit to 1 by software causes an inter-
rupt if enabled . This flag has no meaning in slave mode .
SPICN.4 (WCOL) Write Collision Flag. This bit indicates a write collision when set to 1 . This is caused by
attempting to write to the SPIB while a transfer cycle is in progress . This bit must be cleared
to 0 by software once set . Setting this bit to 1 by software causes an interrupt if enabled .
SPICN.5 (ROVR) Receive Overrun Flag. This bit indicates a receive overrun when set to 1 . This is caused
by two or more characters have been received since the last read by the processor . The
newer data is lost . This bit must be cleared to 0 by software once set . Setting this bit to 1 by
software causes an interrupt if enabled .
SPICN.6 (SPIC) SPI Transfer Complete Flag. This bit indicates the completion of a transfer cycle when
set to 1 . This bit must be cleared to 0 by software once set . Setting this bit to 1 by software
causes an interrupt if enabled .
SPICN.7 (STBY) SPI Transfer Busy Flag. This bit is used to indicate the current status of the SPI module .
STBY is set to 1 when starting a SPI transfer cycle and is cleared to 0 when the transfer
cycle is completed . This bit is controlled by hardware and is read-only for user software .
PR0 (08h, 03h) Phase Register 0
Initialization: The phase register is cleared to 0000h on all forms of reset .
Read/Write Access: Unrestricted read/write .
PR0.15 to PR0.0 Phase Register Bits 15:0. This register is used to load and read the 16-bit value in the
phase register that determines the baud rate for the serial port 0 .