Rainbow Electronics MAXQ3108 - Manual (Page 41)

MAXQ3108
Low-Power, Dual-Core Microcontroller
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Special Function Register Bit Descriptions (continued)
MC0R (09h, 03h) Multiplier Read Register 0
Initialization: This register is cleared to 0000h on all forms of reset.
Read/Write Access: Unrestricted read-only.
MC0R.[15:0]:
Multiplier Read Register 0 Bit 15:0. During multiplication, the MC0R register represents bytes 1
and 0 result from the last operation when MCW bit is 1 or the last operation is either multiply-only
or multiply-negate. When MCW bit is 0 and the last operation is either multiply-accumulate or
multiply-subtract, the contents of this register may or may not agree with the contents of MC0 due
to the combinatorial nature of the adder. The contents of this register remain until a SFR content
related to the multiplier has been changed.
SPICN (0Dh, 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 a logic 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 interrupt 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 that 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 an 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.