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STP2002QFP
Fast Ethernet, Parallel Port, SCSI (FEPS) - STP2002QFP
Sun Microsystems,
The desired handshake protocol can be selected using the ACK_OP
(acknowledge operation) andBUSY_OP (busy operation) bits of the opera-
tions configuration register (OCR). The function of these bits is defined as
follows:
These two bits allow selection of one of four possible protocols, however
only three of these protocols make sense and are valid selections. The case of
ACK_OP=BUSY_OP=1, is not supported. For all protocol selections, if
P_BSY (PP_BSY) is active, further data transfers will not occur untilP_BSY
(PP_BSY) is negated. The following table summarizes the protocol defini-
tions for transfers to the peripheral device.
The transfer modes are shown and discussed in the following sections.
4.3.1.1.1 No Handshake (BUSY_OP=0, ACK_OP=0)
Data transfers are controlled by the use of P_D_STRB (PP_STB) and option-
allyP_BSY (PP_BSY). There is no acknowledge in this mode and P_ACK
(PP_ACK) is a don’t care.P_BSY (PP_BSY) is used to gate further transfers
Table 7:
SBus Clock DSS DSW
16.67 MHz 0–7.62µs 180.0 ns–7.62µs
20 MHz 0–6.35µs 150.0 ns–6.3µs
25 MHz 0–5.08µs 120.0 ns–5.08µs
ACK_OP 1 = Handshake complete with receipt of P_ACK (PP_ACK).
0 = P_ACK (PP_ACK) is ignored.
BUSY_OP 1 = Handshake complete with receipt ofP_BSY (PP_BSY).
0 =P_BSY (PP_BSY) is not used for handshaking.
Table 8:
BUSY_OP ACK_OP Protocol Definition
0 0 No handshaking occurs
0 1 Acknowledge is required for each byte transferred
10P_BSY is used as acknowledge and is required for each byte
transferred. ACK is ignored
1 1 Invalid