Legacy-Free Keyboard/Embedded Controller with SPI and LPC Docking Interface
1. When the transmitter bit time (time between falling edges) exceeds 300us.
2. When the transmitter start bit is not received within 25ms from signaling a transmit start event.
3. If the time from the 1st (start) bit to the 10th (parity) bit exceeds 2ms.
RD_DATA
Read DATA bit: Reading this bit returns the current level of the PS2 channel’s Serial DATA pin. This
bit is used for receiving bit-banged data over the PS2 channel. Bit-banging of the PS2 channel is
enabled when the PS2_EN bit is set to 0. To receive data properly using this bit, PS2_EN must be set
to 0 and the WR_DATA bit in the PS2 Channel’s Control Register must be set to 1.
RD_CLK
Read CLK bit: Reading this bit returns the current level of the PS2 channel’s Serial CLK pin. This bit
is used when receiving bit-banged data over the PS2 channel. Bit-banging of the PS2 channel is
enabled when the PS2_EN bit is set to 0. To receive bit banged data properly, the PS2_EN must be
set to 0 and the WR_CLK bit in the PS2 Channel’s Control Register must be set to 1.
Note 14.24 When PS2_EN = 0, high to low transitions on the CLK pin will generate a PS2 Chan
interrupt. A timeout event or writing this bit low will not cause an interrupt.
Note 14.25 When PS2_EN=1, bit-banging is disabled for any of the following 3 conditions:
Time-out is active.
300us following a time-out (Hold Time).
RDATA_RDY = 1.
14.3.5 SMSC PS/2 Status_2 Registers
Table 14.8 SMSC PS/2_Status_2 Register
-
HOST ADDRESS
8051 ADDRESS
POWER
0x7F48
VCC2
0x00
DEFAULT
D7
D6
D5
D4
D3
D2
D1
D0
-
-
-
-
-
-
-
-
HOST TYPE
8051 TYPE
R/WC
R
R/WC
R
R/WC
R
R/WC
R
XMIT_ST RX_BUSY XMIT_ST RX_BUSY XMIT_ST RX_BUSY XMIT_ST RX_BUSY
BIT NAME
ART_TIM
EOUT_D
D
ART_TIM
EOUT_C
C
ART_TIM
EOUT_B
B
ART_TIM
EOUT_A
A
PROGRAMMER’S NOTE: Always check that an SMSC PS/2 channel is idle, i.e. the RX_BUSY bit is ”0”, before
attempting to transmit on that channel. Receive data may or may not be lost by setting
an SMSC PS/2 channel to transmit while the RX_BUSY bit is asserted depending where
in the message frame the transmit mode change occurs.
RX_BUSY
SMSC LPC47N350
163
Revision 1.1 (01-14-03)
DATASHEET
SMSC [ SMSC CORPORATION ]
