Z8FMC04100 ZILOG [Zilog, Inc.], Z8FMC04100 Datasheet - Page 176

• Manufacturer Part Number: Z8FMC04100
• Description: Z8 Encore-R Motor Control Flash MCUs
• Manufacturer: ZILOG [Zilog, Inc.]

154
Z8 Encore!
Product Specification
Serial Peripheral Interface
Multimaster Operation
®
Motor Control Flash MCUs
Transfer Format Phase Equals One
Figure 26 illustrates the timing diagram for an SPI transfer in which
waveforms are depicted for SCK, one for CLKPOL reset to 0, and another for CLKPOL set
to 1.
Figure 26. SPI Timing When Phase is 1
In a multimaster SPI system, all SCK pins are tied together, all MOSI pins are tied
together, and all MISO pins are tied together. All SPI pins must then be configured in
OPEN-DRAIN mode to prevent bus contention. At any time, only one SPI device is con-
figured as the master and all other SPI devices on the bus are configured as slaves. The
master enables a single slave by asserting the SS pin on that slave only. Then, the single
master drives data out its SCK and MOSI pins to the SCK and MOSI pins on the slaves
(including those which are not enabled). The enabled slave drives data out its MISO pin to
the MISO master pin.
For a master device operating in a multimaster system, if the SS pin is configured as an
input and is driven Low by another master, the COL bit is set to 1 in the SPI Status Regis-
ter. The COL bit indicates the occurrence of a multimaster collision (mode fault error con-
dition).
Input Sample Time
(CLKPOL = 0)
(CLKPOL = 1)
MOSI
MISO
SCK
SCK
SS
P R E L I M I N A R Y
Bit 7
Bit 7
Bit 6
Bit 6
Bit 5
Bit 5
Bit 4
Bit 4
Bit 3
Bit 3
Bit 2
Bit 2
PHASE
Bit 1
Bit 1
PS024604-1005
is 1. Two
Bit 0
Bit 0