12.2.3Synchronous Serial Transmit 1 Register (SSD1, Offset 14h) Synchronous Serial Transmit 0 Register (SSD0, Offset 16h)

The Synchronous Serial Transmit 1 and 0 registers contain data to be transferred from the processor to the peripheral on a write operation. Only the least-significant 8 bits of the register are used. The format of SSD1 and SSD0 is shown in Figure 12-3.

Writes to SSD1 or SSD0 cause the PB bit in the SSS register to be set and a transmission sequence to begin as shown in Figure 12-5 on page 12-8.A write to either SSD1 or SSD0 while the port is busy sets the RE/TE (Receive/Transmit Error) bit in the SSS register and does not generate additional data transfers.

Figure 12-3 Synchronous Serial Transmit Register (SSD1, SSD0, offsets 14h and 16h)

15

7

0

Reserved

SD

The value of these registers at reset is undefined.

Bits 15–8: Reserved —Set to 0.

Bits 7–0: Send Data (SD) —Data to transmit over the SDATA pin. Bit 0 is transmitted first, bit 7 is transmitted last.

Synchronous Serial Interface

12-5

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AMD Am188TMER, Am186TMER user manual Bits 15-8 Reserved -Set to, Synchronous Serial Interface 12-5