Texas Instruments TMS380C26 - Manual (Page 10)

TMS380C26
NETWORK COMMPROCESSOR
SPWS010A–APRIL 1992–REVISED MARCH 1993
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10
Terminal Functions (continued)
System Interface – Intel Mode (SI/M = H)
PIN NAME NO. I/O DESCRIPTION
SDDIR 38 OUT
System Data Direction. This output provides to the external data buffers a signal indicating the direction
in which the data is moving. During DIO writes and DMA reads, SDDIR is low (data direction input to
the TMS380C26). During DIO reads and DMA writes, SDDIR is high (data direction output from the
TMS380C26). When the system interface is
NOT involved in a DIO or DMA operation, then SDDIR is
high by default.
DATA
SDDIR DIRECTION DIO DMA
H output read write
L input write read
SHLDA/SBGR 37 IN
System Hold Acknowledge. This pin indicates that the system DMA hold request has been
acknowledged. It is internally synchronized to SBCLK (see Note 1).
H = Hold request acknowledged.
L
= Hold request not acknowledged.
SHRQ/SBRQ 56 OUT
System Hold Request. This pin is used to request control of the system bus in preparation for a DMA
transfer. This pin is internally synchronized to SBCLK.
H = System bus requested.
L
= System bus not requested.
SIACK 24 IN
System Interrupt Acknowledge. This signal is from the host processor to acknowledge the interrupt
request from the TMS380C26.
H = System interrupt not acknowledged (see Note 1).
L
= System interrupt acknowledged: the TMS380C26 places its interrupt vector onto the system
bus.
SI/M 35 IN
System Intel/Motorola Mode Select. The value on this pin specifies the system interface mode.
H = Intel-compatible interface mode selected. Intel interface can be 8-bit or 16-bit mode
(see S8/SHALT pin description and Note 1.)
L = Motorola-compatible interface mode selected.
SINTR/SIRQ 36 OUT
System Interrupt Request. TMS380C26 activates this output to signal an interrupt request to the host
processor.
H = Interrupt request by TMS380C26.
L
= No interrupt request.
SOWN 59 OUT
System Bus Owned. This signal indicates to external devices that TMS380C26 has control of the
system bus. This signal drives the enable signal of the bus transceiver chips, which drive the address
and bus control signals.
H = TMS380C26 does not have control of the system bus.
L
= TMS380C26 has control of the system bus.
SPH 62 I/O
System Parity High. The optional odd-parity bit for each address or data byte transmitted over
SADH0-SADH7 (see Note 1).
SPL 55 I/O
System Parity Low. The optional odd-parity bit for each address or data byte transmitted over
SADL0-SADL7 (see Note 1).
NOTE 1: Pin has an internal pullup device to maintain a high voltage level when left unconnected (no etch or loads).