Cirrus Logic CS61884 - Manual (Page 33)

CS61884
DS485F3 33
As illustrated in Figure 13 , the ACB consists of a
R/W bit, address field, and two reserved bits. The
R/W bit specifies if the current register access is a
read (R/W = 1) or a write (R/W = 0) operation. The
address field specifies the register address from
0x00 to 0x1f.
13.3 Parallel Port Operation
Parallel port host mode operation is selected when
the MODE pin is high. In this mode, the CS61884
register set is accessed using an 8-bit, multiplexed
bidirectional address/data bus D[7:0]. Timing over
the parallel port is independent of the transmit and
receive system timing.
The device is compatible with both Intel and Mo-
torola bus formats. The Intel bus format is selected
when the MOT/INTL pin is high and the Motorola
bus format is selected when the MOT/INTL pin is
low. In either mode, the interface can have the ad-
dress and data multiplexed over the same 8-bit bus
or on separate busses. This operation is controlled
with the MUX pin; MUX = 1 means that the paral-
lel port has its address and data multiplexed over
the same bus; MUX = 0 defines a non-multiplexed
bus. The timing for the different modes are shown
in
Figure 26 , Figure 27 , Figure 28 , Figure 29 ,
Figure 30 , Figure 31 , Figure 32 and Figure 33 .
Non-multiplexed Intel and Motorola modes are
shown in
Figure 30 , Figure 31 , Figure 32 and
Figure 33 . The CS pin initiates the cycle, followed
by the DS, RD or WR pin. Data is latched into or
out of the part using the rising edge of the DS, WR
or RD pin. Raising CS ends the cycle.
Multiplexed Intel and Motorola modes are shown
in
Figure 26 , Figure 27 , Figure 28 and Figure 29 . A
read or write is initiated by writing an address byte
to D[7:0]. The device latches the address on the
falling edge of ALE(AS). During a read cycle, the
register data is output during the later portion of the
RD or DS pulses. The read cycle is terminated and
the bus returns to a high impedance state as RD
transitions high in Intel timing or DS transitions
high in Motorola timing. During a write cycle, val-
id write data must be present and held stable during
the WR or DS pulses.
In Intel mode, the RDY output pin is normally in a
high impedance state; it pulses low once to ac-
knowledge that the chip has been selected, and high
again to acknowledge that data has been written or
read. In Motorola mode, the ACK pin performs a
similar function; it drives high to indicate that the
address has been received by the part, and goes low
again to indicate that data has been written or read.
CS
SDI
SCLK
SDO
CLKE=0
0 R/W 0 0 0 0 0 1 D0 D1 D2 D5 D3 D6 D4 D7
D0 D1 D2 D5 D3 D6 D4 D7
Address/Command Byte Data Input/Output
Figure 13. Serial Read/Write Format (SPOL = 0)