ez80f92 ZiLOG Semiconductor, ez80f92 Datasheet - Page 141

• Manufacturer Part Number: ez80f92
• Description: Ez80acclaim Flash Microcontrollers
• Manufacturer: ZiLOG Semiconductor

PS015313-0508
SPI Flags
SPI Baud Rate Generator
Mode Fault
The Mode Fault flag (MODF) indicates that there may be a multimaster conflict for sys-
tem control. The MODF bit is normally cleared to 0 and is only set to 1 when the master
device’s SS pin is pulled Low. When a mode fault is detected, the following occurs:
1. The MODF flag (SPI_SR[4]) is set to 1.
2. The SPI device is disabled by clearing the SPI_EN bit (SPI_CTL[5]) to 0.
3. The MASTER_EN bit (SPI_CTL[4]) is cleared to 0, forcing the device into SLAVE
4. If the SPI interrupt is enabled by setting IRQ_EN (SPI_CTL[7]) High, an SPI
Clearing the Mode Fault flag is performed by reading the SPI Status register. The other
SPI control bits (SPI_EN and MASTER_EN) must be restored to their original states by
user software after the Mode Fault flag is cleared.
Write Collision
The WRITE COLLISION flag, WCOL (SPI_SR[5]), is set to 1 when an attempt is made
to write to the SPI Transmit Shift register (SPI_TSR) while data transfer occurs. Clearing
the WCOL bit is performed by reading SPI_SR with the WCOL bit set.
The SPI’s Baud Rate Generator creates a lower frequency clock from the high-frequency
system clock. The Baud Rate Generator output is used as the clock source by the SPI.
Baud Rate Generator Functional Description
The SPI’s Baud Rate Generator consists of a 16-bit downcounter, two 8-bit registers, and
associated decoding logic. The Baud Rate Generator’s initial value is defined by the two
BRG Divisor Latch registers, {SPI_BRG_H, SPI_BRG_L}. At the rising edge of each
system clock, the BRG decrements until it reaches the value
clock rising edge, the BRG reloads the initial value from {SPI_BRG_H, SPI_BRG_L) and
outputs a pulse to indicate the end-of-count. Calculate the SPI Data Rate with the follow-
ing equation:
SPI Data Rate (bps)
mode.
interrupt is generated.
=
System Clock Frequency
2 X SPI Baud Rate Generator Divisor
0001h
Product Specification
Serial Peripheral Interface
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