UART Modules
MCF52110 ColdFire® Integrated Microcontroller Reference Manual, Rev. 1
23-12
Freescale Semiconductor
Preliminary
23.3.7
UART Transmit Buffers (UTB
n
)
The transmit buffers consist of the transmitter holding register and the transmitter shift register. The
holding register accepts characters from the bus master if UART’s USR
n
[TXRDY] is set. A write to the
transmit buffer clears USR
n
[TXRDY], inhibiting any more characters until the shift register can accept
more data. When the shift register is empty, it checks if the holding register has a valid character to be sent
(TXRDY equals 0). If there is a valid character, the shift register loads it and sets USR
n
[TXRDY] again.
Writes to the transmit buffer when the UART’s TXRDY equals 0 and the transmitter is disabled have no
effect on the transmit buffer.
shows UTB
n
. TB contains the character in the transmit buffer.
23.3.8
UART Input Port Change Registers (UIPCR
n
)
, hold the current state and the change-of-state for UCTS
n
.
IPSBAR
Offset:
0x00_020C (URB0)
0x00_024C (URB1)
0x00_028C (URB2)
Access: User read-only
7
6
5
4
3
2
1
0
R
RB
W
Reset:
1
1
1
1
1
1
1
1
Figure 23-8. UART Receive Buffer (URB
n
)
IPSBAR
Offset:
0x00_020C (UTB0)
0x00_024C (UTB1)
0x00_028C (UTB2)
Access: User write-only
7
6
5
4
3
2
1
0
R
W
TB
Reset:
0
0
0
0
0
0
0
0
Figure 23-9. UART Transmit Buffer (UTB
n
)
IPSBAR
Offset:
0x00_0210 (UIPCR0)
0x00_0250 (UIPCR1)
0x00_0290 (UIPCR2)
Access: User read-only
7
6
5
4
3
2
1
0
R
0
0
0
COS
1
1
1
CTS
W
Reset:
0
0
0
0
1
1
1
UCTS
n
Figure 23-10. UART Input Port Changed Registers (UIPCR
n
)