Table of Contents
Advertisement
characters until the shift register is ready to accept more data. When the shift register is
empty, it checks to see if the holding register has a valid character to be sent (TxRDY bit
cleared). If there is a valid character, the shift register loads the character and reasserts
the TxRDY bit in the channel's SR. Writes to the transmitter buffer when the channel's SR
TxRDY bit is clear and when the transmitter is disabled have no effect on the transmitter
buffer. This register can only be written when the serial module is enabled (i.e., the STP
bit in the MCR is cleared).
TB7–TB0—These bits contain the character in the transmitter buffer.
7.4.1.10 INPUT PORT CHANGE REGISTER (IPCR). The IPCR shows the current state
and the change-of-state for the CTSA and CTSB pins. This register can only be read
when the serial module is enabled (i.e., the STP bit in the MCR is cleared).
Bits 7, 6, 3, 2—Reserved
COSB, COSA—Change-of-State
1 = A change-of-state (high-to-low or low-to-high transition), lasting longer than 25–
50 s when using a crystal as the sampling clock or longer than one or two
periods when using SCLK, has occurred at the corresponding CTS input (MCR
ICCS bit controls selection of the sampling clock for clear-to-send operation).
When these bits are set, the ACR can be programmed to generate an interrupt to
the CPU32.
0 = The CPU32 has read the IPCR. No change-of-state has occurred. A read of the
IPCR also clears the ISR COS bit.
CTSB, CTSA—Current State
Starting two serial clock periods after reset, the CTS bits reflect the state of the CTS
pins. If a CTS pin is detected as asserted at that time, the associated COSx bit will be
set, which will initiate an interrupt if the corresponding IECx bit of the ACR register is
enabled.
1 = The current state of the respective CTS input is negated.
0 = The current state of the respective CTS input is asserted.
MOTOROLA
Freescale Semiconductor, Inc.
TBA, TBB
7
6
5
4
TB7
TB6
TB5
TB4
RESET:
0
0
0
0
Write Only
IPCR
7
6
5
4
0
0
COSB
COSA
RESET:
0
0
0
0
Read Only
MC68340 USER'S MANUAL
For More Information On This Product,
Go to: www.freescale.com
$713, $71B
3
2
1
0
TB3
TB2
TB1
TB0
0
0
0
0
Supervisor/User
$714
3
2
1
0
0
0
CTSB
CTSA
0
0
U
U
Supervisor/User
7- 31
Advertisement
Table of Contents
