MPC555
/
MPC556
SIGNAL DESCRIPTIONS
MOTOROLA
USER’S MANUAL
Rev. 15 October 2000
2-15
Transfer size –
Indicates the size of the requested data transfer in the current bus cy-
cle.
2.3.1.11 RD/WR
Pin Name
: rd_wr_b
Read/Write –
Indicates the direction of the data transfer for a transaction. A logic one
indicates a read from a slave device; a logic zero indicates a write to a slave device.
2.3.1.12 BURST
Pin Name
: burst_b
Burst Indicator –
Indicates whether the current transaction is a burst transaction or
not.
2.3.1.13 BDIP
Pin Name
: bdip_b
Burst data in progress –
Indicates to the slave that there is a data beat following the
current data beat.
2.3.1.14 TS
Pin Name
: ts_b
Transfer Start –
Indicates the start of a bus cycle that transfers data to/from a slave
device. This signal is driven by the master only when it gained the ownership of the
bus. Every master should negate this signal before the bus relinquish. Every master
should negate this signal before the bus is relinquished. This pin is an active negate
signal and may need an external pull-up resistor to ensure proper operation and signal
timing specifications.
2.3.1.15 TA
Pin Name
: ta_b
Transfer Acknowledge –
This line indicates that the slave device addressed in the
current transaction has accepted the data transferred by the master (write) or has driv-
en the data bus with valid data (read). The slave device negates the TA_B signal after
the end of the transaction and immediately three-state it to avoid contentions on the
line if a new transfer is initiated addressing other slave devices. This pin is an active
negate signal and may need an external pull-up resistor to ensure proper operation
and signal timing specifications.
2.3.1.16 TEA
Pin Name
: tea_b
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Freescale Semiconductor, Inc.
For More Information On This Product,
Go to: www.freescale.com
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