AP522 ACROPACK
USER
’S MANUAL
Acromag, Inc. Tel: 248-295-0310
- 47 - http://www.acromag.com
- 47 -
www.acromag.com
3.4.15 Transmit FIFO Level Counter
–
Read Only
Transmit FIFO level byte count from 0x00 (0 bytes) to 0xFF (255 or 256
bytes). This 8-bit register gives an indication of the number of characters in
the transmit FIFO. The FIFO level Byte count register is read only. The user
can take advantage of the FIFO level byte counter for faster data loading to
the transmit FIFO, which reduces CPU bandwidth requirements.
3.4.16 Transmit FIFO Trigger Level
–
Write Only
An 8-bit value written to this register sets the TX FIFO trigger level from 0x01
(one) to 0xFF (255). A value of 0x00 is invalid. The TX FIFO trigger level
generates an interrupt whenever the data level in the transmit FIFO falls
below this preset trigger level.
3.4.17 Receive FIFO Level Counter
–
Read Only
Receive FIFO level byte count from 0x00 (zero) to 0xFF (255). It gives an
indication of the number of characters in the receive FIFO. The FIFO level
byte count register is read only. The user can take advantage of the FIFO level
byte counter for faster data unloading from the receiver FIFO, which reduces
CPU bandwidth requirements.
3.4.18 Receive FIFO Trigger Level
–
Write Only
An 8-bit value written to this register, sets the RX FIFO trigger level from 0x01
(one) to 0xFF (255). A value of 0x00 is invalid. The RX FIFO trigger level
generates an interrupt whenever the receive FIFO level rises to this preset
trigger level.
3.4.19 XOFF1, XOFF2, XON1 and XON2 Registers
–
Write Only
These registers are used to program the Xoff1, Xoff2, Xon1 and Xon2 control
characters respectively.
3.4.20 XCHAR Register
–
Read Only
This register gives the status of the last sent control character (Xon or Xoff)
and the last received control character (Xon or Xoff). This register will be
reset to 0x00 if, at any time, the Software Flow Control is disabled.
Table 3.23 XCHAR Register
XCHAR
Bit
FUNCTION PROGRAMMING
0
XOFF
Detect
Indicator
If the last received control character was a Xoff
character or characters (Xoff1, Xoff2), this bit will
be set to a logic 1. This bit will clear after the read.
1
XON
Detect
Indicator
If the last received control character was a Xon
character, Xon characters (Xon1, Xon2) or an Xon-
Any character, this bit will be set to a logic 1. This
